Thousands of angry demonstrators rallied outside the U.S. Embassy in China. (Reuters)

BEIJING, May 9 (Sunday) – Anti-American demonstrations rocked Chinese cities for a second day Sunday as tens of thousands of Chinese students attacked and in one case burned U.S. diplomatic installations to protest the deadly bombing of China's embassy in Yugoslavia.

Carrying banners that said "Down with NATO!" "Down with American imperialism!" and "Clinton equals Hitler," thousands of protesters again surrounded the U.S. Embassy in Beijing, tossing black and red paint bombs at the building and smashing most of its windows with rocks. Several youths scaled the fence and attempted to rip down the American flag but were forced out by Chinese riot police. The nationwide demonstrations, a mixture of officially sanctioned and spontaneous outpourings, underscore the most serious crisis in U.S.-China relations since ties were established in 1979.

"We used to think the United States was a model," said Wang Fei, a 33-year-old graduate of Stanford University as he marched today, "But now you've killed our people. This is the end of our honeymoon with America."

Protests erupted in Chengdu, Guangzhou, Shanghai, Changsha, Hangzhou and other cities with witnesses reporting thousands of people massing in those cities against the United States and NATO. In the southwestern city of Chengdu, protesters ransacked an burned the consulate general's residence, said a U.S. Embassy spokesman in Beijing. The protests were generally approved by the Chinese government, but several government officials said they feared the protests could turn violent. Other officials said they were concerned that political dissidents might attempt to manipulate the genuine fury of the students to call for political changes in China. Exactly 10 years ago, massive pro-democracy protests brought life in Beijing to a standstill until government troops launched a bloody crackdown.

China rejected NATO's explanation that the attack was a mistake. In a front-page editorial in Sunday's editions of the People's Daily, read on the late night news Saturday, the Communist Party's mouthpiece called NATO's account "chicanery . . . that could not cover up the bloodstained facts."

"The Chinese government has stated that it reserves the right to take further action," the editorial warned. "This was the wild behavior of an aggressor." Other official newspapers Sunday morning further fanned the flames of anti-American feeling, "China has become the main obstacle to the United States and other NATO countries promoting hegemony in Asia," said the Beijing Morning Post, which said the embassy attack was deliberate. "The top priority of the United States in Asia is to contain China."

Ties between the United States and China have been deteriorating since last year. But the NATO strike on the embassy in Belgrade, killing three Chinese journalists, is likely to be a serious setback for cooperation on a number of fronts, Chinese and Western officials predicted.

The attack could compromise Washington's ability to get China's help in the U.N. Security Council for approval of an international peacekeeping force for Kosovo. Cooperation against nuclear weapons proliferation on the Korean peninsula also could suffer. Washington's attempts to get China into the World Trade Organization, already faltering, may be further at risk.

On Saturday night here, a sense that U.S. policy continued to drift with regard to China persisted as one Chinese official complained that Ambassador James R. Sasser had not made a public statement of regret. "Who do you think we are?" asked the official. "What are your diplomats for?"

Several hours later, in Washington, the State Department issued a statement saying Sasser had conveyed America's condolences and remorse to the Chinese Foreign Ministry in Beijing.

"The United States deeply regrets the loss of life and injuries" caused by the "accidental bombing" of the embassy, the statement said. U.S. officials said they had protested to China that their diplomatic missions in China were not being adequately protected.

On a deeper level, the marches illustrated the risk posed to the attraction between China's people and the United States – an attraction that has bedeviled China's authoritarian government since Americans began flocking to China in large numbers in the 1980s. While rage at the United States was a common emotion – especially when the news came that a newlywed couple was among China's dead – the most significant sentiment was deep disappointment.

Shao Yafeng, a 26-year-old graduate student in economics at Beijing University, said his first thought was that the Americans couldn't have done it. A terrorist must have been to blame, he considered. Multiple hits by U.S. bombs convinced him.

"I feel very sad. . . . I have watched so many American movies and other things," he said while marching around the U.S. Embassy Saturday afternoon. "I believe America has so much that is so humane, and so just. And the spirit of the individual. I would never have thought something like this would happen."

"You were the ideal for so many of us," added one senior Chinese official, who was marching alongside workers in Saturday night's spontaneous marches. "And now your stupid bombs have killed our people. This could set us back years. This is a perfect justification for slowing reforms, for closing political debate. And it's really your fault."

China's state-run media sought to take advantage of the attacks. In every reference, NATO was "American-led." U.S. ideals about human rights were "empty in the face of the barbarous bombing."

Perhaps most significant was the wholesale rejection by China's state-run media of NATO's explanation that it made a mistake. China's television stations, its main newspaper and the protesters all seemed to believe that the attack was carried out on purpose – part of a complicated conspiracy to keep China weak.

The daughter of one high-ranking official said she talked with several military officers who were convinced that NATO wanted to attack the embassy. "I told them it had to have been a mistake but they said, 'No way, U.S. technology is just too good.' "

NATO, a 19-member alliance in which the United States is the most powerful member, said the four laser-guided bombs targeted the embassy in a case of mistaken identity. It said the bombs were supposed to be aimed at a nearby Yugoslav military supply building, which Belgrade residents said was of similar size and age as the Chinese mission.

The NATO attack came at a time when China had started to modify its criticism of the aerial onslaught of Yugoslavia, partly as a response to its own problems with restive Tibetans and Muslim Uighurs and partly to its desire to placate the Muslim world. Now, Chinese journalists predicted, that moderation will evaporate.

The demonstrations also came at a sensitive time for China internally. Ten years ago, on June 4th, Chinese soldiers crushed a student-led movement around Beijing's Tiananmen Square – protests very much inspired by the ideals of American democracy. The government has made intense efforts to prevent any commemoration of that crackdown, rounding up dozens of dissidents and blocking satellite TV signals into China among other moves. Nonetheless, it approved Saturday's protests, possibly reasoning that a fierce round of anti-American propaganda would help dampen any residual enthusiasm for commemorating Tiananmen. Saturday's protests were by far the largest in China since the 1989 demonstrations. According to the official New China News Agency, tens of thousands protested around the U.S. Consulate in Chengdu, 15,000 did so in Shanghai and tens of thousands in the southern metropolis of Guangzhou. By early Sunday in Beijing, more than 10,000 protesters were estimated to have passed through the diplomatic area near the U.S. Embassy. Xian, Wuhan and Chongqing, as well as Hong Kong, were among other cities where protests exploded.

In Beijing, the initial protest was led by the Beijing City Student Association, an official government group. But hundreds of other students, including those who couldn't fit on the buses, some from schools not officially involved, recent alumni and ordinary citizens, eluded a wide but porous police perimeter around the area to join the marches.

Many learned about the initial demonstrations on a popular Web site, www.sina.com, a Sino-American joint-venture portal with a widely read bulletin board. Many others flocked to the area after calls from from friends with mobile phones.

Hundreds of police lined the streets but did not interfere with the students or their rock throwing. Even when the protesters broke embassy windows and the large street lamps with rocks and pieces of pavement, police stood by without taking action. A roar of cheers erupted each time the shattering of glass was heard. Embassy officials could be seen on the second and third floors of the main embassy building, peering from small windows.

When protesters began smashing U.S. embassy cars late Saturday, however, the police moved in. In the evening, police blocked off access to the main U.S. Embassy compound but let people gather in front of the ambassador's residence.

Zhang Ping, a 45-year-old machine worker, came to the protest Saturday night with his wife. Police had started to block off the U.S. Embassy and move demonstrators away from the neighborhood. "Patriotism is not a crime," chanted the crowd. "Let's blow up the U.S. Embassy!"

"Simply apologizing won't satisfy China's people. The war criminals must be tried. If China bombed the American Embassy and made a simple apology, would that be all right?" Zhang asked.

Then echoing a tone that could be heard throughout the night, he said: "In the years since the end of the Qing Dynasty, China has been trampled on by foreign powers. Today's Chinese people absolutely will not accept such a humiliation."

Among the crowd were veterans of the Tiananmen movement. One, a student-leader-turned-businessman who cheered when the U.S. Embassy was being pelted with rocks, predicted that if "China sent a supporting army over there [to Yugoslavia], many people would volunteer."

However, he added that the central government may get "worried" at the ferocity of the protests. "They hope it will not continue for too long because June 4 is coming quickly," he said.

As the demonstrations faded into the night early Sunday, a mechanical engineering major from Qinghua University who identified himself only as Wang confided in a passerby.

"I grew up hearing how China should join this international organization and that international organization. How we should become part of the world," he said. "Sure, I still want all that. But I don't want the world to be an American world. You love violence too much. You need to stop telling the rest of us what to do."

Correspondent Daniel Williams in Belgrade and staff writer John F. Harris in Washington contributed to this report.