HONG KONG — Myanmar's military said Monday that it took control of the country and declared a state of emergency for a year, after detaining civilian leader Aung San Suu Kyi and other leaders of her ruling National League for Democracy (NLD) in a predawn operation, staging a coup against the democratically elected government.

The raids came hours before a new session of parliament was scheduled to open and members who won the November elections were set to take their seats. Suu Kyi’s NLD won those elections in a landslide, capturing 396 out of 476 seats. It was Myanmar’s second democratic election since the country’s fragile transition from military rule to democracy.

NLD spokesman Myo Nyunt told The Washington Post that Suu Kyi, Myanmar President Win Myint and all chief ministers from their party, representing over a dozen states and regions in the country, were taken at gunpoint. A spokesman for his party was also detained, he said.

“I expect that soldiers will arrive for me soon,” Myo Nyunt said. “This is very likely a coup, but we hope that there will also be negotiation between our leaders and the military.”

Several hours after the raids, the military in a television broadcast said that a state of emergency had been declared in Myanmar and that power would be transferred to the commander in chief, Min Aung Hlaing. Myint Swe, a former general and the military-backed vice president, will become the president, the broadcast added.

The sweep also included other prominent democracy activists who have been fighting against military rule for decades, leaders of other political parties and NLD lawmakers, according to social media posts and news reports.

Communications appeared to be down or patchy in Naypyidaw, Myanmar’s capital, as well as in Yangon, the country’s largest city and commercial hub. The state-run broadcaster Myanmar Radio and Television said in a Facebook post that it was not able to broadcast “due to communication problems.” Websites were also down; the Internet monitoring service Netblocks said national connectivity had fallen to 75­ percent of normal levels.

The military has alleged voter fraud in the November vote, but Myanmar’s election commission has said there is no evidence to support its claims. The military’s proxy party, the Union Solidarity and Development Party, also alleged voter fraud after winning only 33 seats.

In Yangon, Myanmar, on Jan. 30, protesters marched in opposition the Nov. 8, 2020, election, which the National League for Democracy won in a landslide. (AP)

Political tensions and fears of a military takeover have prompted alarm in the international community.

In a statement late Sunday in Washington, White House press secretary Jen Psaki said the United States was alarmed by the reports and urged Myanmar’s military to adhere to the rule of law and release those detained, or face consequences. “The United States opposes any attempt to alter the outcome of recent elections or impede Myanmar’s democratic transition, and will take action against those responsible if these steps are not reversed,” she said.

Secretary of State Antony Blinken added in a statement that Washington stood with the people of Myanmar, also known as Burma, in their “aspirations for democracy, freedom, peace, and development.”

United Nations Secretary-General Antonio Guterres strongly condemned the events and expressed grave concern about the “serious blow to democratic reforms in Myanmar,” his spokesman said.

On Friday, diplomatic missions in Myanmar affirmed their support for the country’s democratic transition and urged the military to respect the results of the elections.

The military, known as the Tatmadaw, said diplomats were making “unwarranted assumptions” and denied it was impeding the democratic transition.

Myanmar’s military ruled the country for a half-century before beginning a celebrated transition to democracy in 2010 and allowing elections in 2015 that ushered Suu Kyi and her party to power. But the current military-drafted constitution enshrines power for military generals, who have a quarter of seats in parliament and maintain control over key ministries.

Suu Kyi spent 15 years under house arrest before her release in November 2010, and won the Nobel Peace Prize in 1991 for her resistance to military rule. The military-drafted constitution prevents her from leading Myanmar as president, but she is unequivocally the nation’s leader, revered as a deity, and rules through proxies. The military-drafted constitution also allows the army to step in in a situation that may “disintegrate” the country and national solidarity.

Since taking power, though, she has disappointed old allies in the West, particularly for defending Myanmar — and its military in particular — against charges of genocide over the persecution of the Rohingya ethnic minority. Suu Kyi has in recent years moved closer toward powers such as China and India, and grown increasingly estranged from countries such as the United States and Britain, which once led advocacy efforts to get her released from house arrest.

The historian and writer Thant Myint-U said Monday that “the doors just opened to a very different future.”

“I have a sinking feeling that no one will really be able to control what comes next,” he tweeted. “And remember Myanmar’s a country awash in weapons, with deep divisions across ethnic & religious lines, where millions can barely feed themselves.”

Kyaw Ye Lynn reported from Yangon, Myanmar. Timothy McLaughlin in Hong Kong contributed to this report.