Washington on Tuesday formally designated Myanmar's military ouster of Aung San Suu Kyi's government as a coup, after the country's army chief General Min Aung Hlaing described the takeover as "inevitable".
Myanmar's powerful military on Monday detained Suu Kyi and other National League for Democracy (NLD) party leaders in pre-dawn raids ahead of a scheduled resumption of parliament.
General Min Aung Hlaing was given "legislative, judicial and executive powers", effectively returning Myanmar to military rule after a 10-year experiment with democracy.
In his first public comments since the putsch, the general said the military takeover was "in line with the law" after the government failed to respond to its grievances over alleged electoral fraud.
"After many requests, this way was inevitable for the country and that's why we had to choose it," he said during the first cabinet meeting, according to a speech posted on the military's official Facebook page.
In Washington, the State Department said it had assessed that "Aung San Suu Kyi, the leader of (Myanmar's) ruling party, and Win Myint, the duly elected head of government, were deposed in a military coup."
The designation means the US cannot assist the Myanmar government, though any impact will be mainly symbolic as almost all assistance goes to non-governmental entities. The military was already under US sanctions over its brutal campaign against the Rohingya minority.
- Pots and pans -
In the capital Naypyidaw, armed troops were stationed outside the dormitories for parliamentarians.
One NLD lawmaker described it as "an open-air detention centre", though by nightfall some politicians said they were free to leave.
A statement on the NLD's verified Facebook page called for Suu Kyi's release, as well as that of President Win Myint and all detained party members.
It also demanded the military "recognise the confirmed result of the 2020 general election".
By afternoon, a party officer said there had been no direct contact with Suu Kyi, though a neighbour saw her in her Naypyidaw residence.
"She walks sometimes in her compound to let others know she's in good health," NLD press officer Kyi Toe told AFP.
On Tuesday evening, in the country's commercial hub of Yangon, residents honked car horns and clattered pots and pans in protest at the coup, following a social media campaign.
Some chanted "Long live Mother Suu".
- Condemnation -
The military has alleged widespread fraud in elections held three months ago that the NLD won in a landslide.
It said it would hold power under a state of emergency for 12 months, claiming it would then hold fresh elections -- a vow the army chief repeated during the first cabinet meeting post-coup.
US President Joe Biden has led a chorus of global outrage, calling for a quick restoration of democracy.
UN Secretary-General Antonio Guterres, the European Union and several other nations have also spoken out.
But China's response was less emphatic, with the official Xinhua news agency describing the coup as a "cabinet reshuffle".
The UN Security Council held an emergency meeting Tuesday but failed to agree on a statement condemning the coup.
To be adopted, it requires the support of China, which wields veto power as a permanent Security Council member and is Myanmar's main supporter at the UN.
- Military rule -
Myanmar's November polls were only the second democratic elections the country had held since emerging from the 49-year grip of military rule in 2011.
The NLD won more than 80 percent of the vote -- increasing its support from the 2015 elections.
But the military claimed to have uncovered more than 10 million instances of voter fraud, and signalled last week it was considering a coup.
It strangled the internet as the putsch was unfolding, but eased restrictions later in the day.
There were few signs of extra security in Yangon, Myanmar's biggest city, indicating the generals' belief that, for now, they faced no mass protests.
On the streets, people voiced anger, fear and helplessness.
"We want to go out to show our dissatisfaction," a taxi driver told AFP.
"But Mother Suu is in their hands. We cannot do much but stay quiet at this moment."
Myanmar's youth networks have announced a "civil disobedience" campaign, though it has yet to materialise.
The takeover has some supporters -- on Tuesday, hundreds of pro-military partisans gathered around Yangon's Shwedagon Pagoda in a rousing celebration.
- Pariah -
Though former general Myint Swe is acting president, military chief Min Aung Hlaing is now in charge.
The 64-year-old coup leader is an international pariah under US sanctions for the violent campaign against Myanmar's Muslim Rohinyga community that forced 750,000 of them to flee into Bangladesh, a campaign that UN investigators said amounted to genocide.
Suu Kyi, 75, remains immensely popular in Myanmar for her opposition to the military -- which earned her the Nobel Peace Prize -- having spent the best part of two decades under house arrest during the previous dictatorship.
But her international image collapsed during her time in power as she defended the Rohingya crackdown.
Derek Mitchell, the first US ambassador to Myanmar after military rule, said the international community needed to respect Suu Kyi's overwhelming victory in November.
The West "may have considered her this global icon of democracy and that lustre is off," he said.
"But if you care about democracy in the world, then you must respect the democratic choice and she is clearly that".