Myanmar's military has seized power in a coup against the government of Aung San Suu Kyi, who was detained along with other leaders of National League for Democracy (NLD) party, in early morning raids.
The army said it had carried out the detentions in response to "election fraud", handing power to military chief Min Aung Hlaing and imposing a state of emergency for one year, according to a statement on a military-owned television station. A military spokesman did not answer phone calls seeking further comment.
Phone lines to the capital Naypyitaw and the main commercial centre of Yangon were not reachable, and state TV went off air hours before parliament had been due to sit for the first time since the NLD's landslide election win in November, viewed as a referendum on Suu Kyi's fledgling democratic government.
Soldiers took up positions at city hall in Yangon and mobile internet data and phone services in the NLD stronghold were disrupted, residents said. Internet connectivity also had fallen dramatically, monitoring service NetBlocks said.
The NLD said Suu Kyi called on the public not to accept a coup by the military and urged them to protest.
"The actions of the military are actions to put the country back under a dictatorship," the NLD said in a statement which carried leader Aung San Suu Kyi's name. "I urge people not to accept this, to respond and wholeheartedly to protest against the coup by the military."
Suu Kyi, Myanmar President Win Myint and other NLD leaders had been "taken" in the early hours of the morning.
The detentions came after days of escalating tension between the civilian government and the military that stirred fears of a coup in the aftermath of the election.
The White House said President Joe Biden had been briefed on the arrest of Suu Kyi.
"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," spokeswoman Jen Psaki said in a statement.
The Australian government said it was "deeply concerned at reports the Myanmar military is once again seeking to seize control of Myanmar" and called for the immediate release of the unlawfully detained leaders.
Japan said it was watching the situation and currently had no plans to repatriate Japanese nationals from Myanmar.
Suu Kyi came to power after a 2015 election win that followed decades of house arrest in a struggle for democracy with Myanmar's junta that turned her into an international icon.
Her international standing was damaged after hundreds of thousands of Rohingya fled army operations into refuge from Myanmar's western Rakhine state in 2017, but she remains hugely popular at home.
Political tensions soared last week when a military spokesman declined to rule out a coup ahead of the new parliament convening on Monday, and military chief Min Aung Hlaing raised the prospect of repealing the constitution.
But the military appeared to backtrack on the weekend, issuing a statement on social media on Sunday saying it would "do everything possible to adhere to the democratic norms of free and fair elections".
Tanks were deployed in some streets last week and pro-military demonstrations have taken place in some cities ahead of the first gathering of parliament.
Myanmar's election commission has rejected the military's allegations of vote fraud.
The constitution published in 2008 after decades of military rule reserves 25 per cent of seats in parliament for the military and control of three key ministries in Suu Kyi's administration.