TOKYO, Monday, Nov. 17— South Korea announced today that North Korean loudspeakers along the border had reported that Kim Il Sung, the North's leader, had been shot to death.

The reports could not be independently confirmed, and the North Korean embassies in Peking and New Delhi issued denials, deepening the uncertainty. The embassy in Peking called the report ''a total fabrication.''

In New Delhi, a North Korean diplomat said, ''In my opinion these reports are not true and are actually South Korean propaganda.'' No U.S. Confirmation

A spokesman for United States forces in South Korea said that they had ''no independent confirmation'' that the North Koreans had made any announcement over the loudspeakers across the demilitarized zone. [ In Washington, high-level military sources said the Pentagon had received reports of Mr. Kim's death as early as Saturday. They said no special alert had been ordered for American forces in the region. ] A Cult of Personality The death of Mr. Kim would have a great effect not only on North-South relations in Korea but also on security considerations throughout the region.

Mr. Kim, 74 years old, has led North Korea since the nation was founded in 1948. During his long tenure, he has encouraged a cult of personality that pervades his nation. He is known to North Koreans as the ''Great Leader,'' and his face and his sayings are omnipresent in the country.

In recent years, he has devoted a great deal of effort to promoting the stature of his son, Kim Jong Il, whom he has named as his successor. Kim Jong Il, who is 43, is called by the obligatory title ''Dear Leader.''

According to diplomats in Seoul, the South Korean Government held an emergency meeting this morning headed by Prime Minister Lho Shin Yong. The police were also said to have been put on alert, but Seoul residents said in telephone interviews that activity on the streets of the capital seemed normal.

A North Korean radio broadcast monitored in Tokyo did not mention reports of Mr. Kim's death. The radio continued normal broadcasting all morning.

Nevertheless, diplomats in Tokyo and Seoul scrambled this morning for information. ''I have strong feelings that something has happened,'' a Japanese diplomat in Seoul said in a telephone interview.

Prime Minister Yasuhiro Nakasone of Japan, asked to comment on the reports, was quoted by Reuters as saying: ''I have heard of such information but it has not been confirmed yet. I have instructed the Foreign Ministry to check it.''

The United States military spokesman in South Korea said American forces had noticed no unusual activity along the demilitarized zone and had continued their regular tours. Implacable Enemies

The two Koreas have been implacable enemies since the division of the Korean Peninsula after World War II. For South Koreans, Mr. Kim has been a hated symbol of both Communism and a perceived military threat.

His designation of his son, Kim Jong Il, as his successor could bring about the first dynastic transition in a Communist country and has caused concern among North Korea's principal allies, the Soviet Union and China.

There have been frequent reports from North Korea that the transition to Kim Jong Il was all but complete.

Kim Il Sung's health was reported to have deteriorated in recent years, prompting rumors that his death was imminent or that he was about to turn over full control to his son.

Reports that Mr. Kim had died began circulating Sunday in a dispatch by the Tokyo correspondent for the South Korean newspaper Chosun Ilbo. South Korea Issues Statement

At midmorning today, a South Korean spokesman issued this statement:

''On Nov. 16, the North Korean public address system along the demilitarized zone broadcast that Kim Il Sung, the North Korean ruler, was shot to death, a spokesman for the Ministry of National Defense said today.

''However, the official news media of North Korea have not yet made any announcement or comment on the broadcast. The Republic of Korea's armed forces are, as always, maintaining their state of readiness.''

A Western diplomat in Seoul said that his embassy was aware of unusual movements in North Korea over the weekend and that evidence was accumulating that something important had happened.

''Clearly there is something going on,'' the diplomat said. Referring to Mr. Kim, he added, ''The fragmentary pieces of evidence we have accumulated over the weekend suggest that he may have died, but none of the evidence has been confirmed.''

According to reports from Peking, the North Korean Embassy, in denying the reports, said, ''The South Korean side always spreads such fabrications.''

In Tokyo, a group of Koreans sympathetic to the North also denied the reports. A Tightly Sealed Border

One reason for the lack of clear information is that North Korea's borders are among the most tightly sealed in the world. Few visitors are allowed, and diplomats based in the capital, Pyongyang, say their movements are severely restricted.

President Kim has lived a secretive existence, rarely traveling outside North Korea and moving inside the country with extreme caution. Diplomats in Pyongyang reported in recent years that he rarely slept more than one night at a time in the same place and that arrangements at his palatial headquarters in the eastern suburbs of Pyongyang implied an acute concern for his security.

Travelers found that uniformed men with automatic rifles checked all vehicles at roadblocks more than a mile from the headquarters and allowed only those in Mr. Kim's inner circle to pass. Praise for Leader Is Lavish

Wherever visitors go in North Korea, to hospitals, libraries or the many monuments and museums that honor Mr. Kim, , guides speak of little but his accomplishments. Defectors have reported that the mildest dissent is punished with long terms in labor camps or, in extreme cases, execution without trial.

While falling badly behind the economic accomplishments of South Korea, the North nonetheless has achieved agricultural and industrial successes under Mr. Kim that compare well with other Communist countries in Asia, notably China and Vietnam.

Mr. Kim has also been credited with deft management of the country's relations with the Soviet Union and China, never allowing either to gain a dominant influence. Although he has leaned toward Moscow in the last two years, he has been careful to maintain close contacts with Peking. He has even encouraged a belief that he might imitate some of the market-oriented economic reforms instituted in China by Deng Xiaoping. ASSASSINS REPORTED IN CHINA TOKYO, Monday, Nov. 17 (Reuters) - Japan was told by Chinese sources that Kim Il Sung had been assassinated and that his killers had fled to China, a Japanese official said today.

The official, in charge of intelligence on North Korea, said he had received information on Saturday from Chinese sources that Mr. Kim had been assassinated and that the killers were being held under Chinese protection. But the official added that Japan had been unable to verify the information. CONFUSION IN SEOUL SEOUL, South Korea, Monday, Nov. 17 (AP) - There was no explanation here of why North Korea would report the death of its leader through loudspeakers along the demilitarized zone that divides the peninsula. They are ordinarily used for propaganda broadcasts beamed to the South.

Lee Heung Shik, spokesman for the South Korean Defense Ministry, said that regular North Korean radio broadcasts monitored here had made no mention of such an event, and that no confirmation had been received through other channels.

Police officials announced that the entire national police force had been placed on full alert ''in connection with the recent situation in North Korea and to block possible subversive attempts by impure elements.''

The term ''impure elements'' is often used by authorities here to describe Communists or their supporters.

Photo of Kim Il Sung (Magnum/Hiroji Kubota)