Protesters are deeply sceptical of the junta's assurances, given at a news conference on Tuesday, that there would be a fair election and it would hand over power, even as police filed an additional charge against Suu Kyi.

The Nobel Peace laureate, detained since the February 1 coup, now faces a charge of violating a Natural Disaster Management Law as well as charges of illegally importing six walkie talkie radios. At a hearing by video conference on Tuesday, her next hearing was set for March 1.

"What they said was totally untrue. I don't acknowledge them at all," a protester who gave her name as Khin said of the military's news conference, when it again defended the coup saying a November 8 election, swept by Suu Kyi's party, was fraudulent.

"They said there was vote fraud but look at the people here now," said Khin who was among thousands gathering at the Sule Pagoda, a central protest site in the main city of Yangon.

The army takeover has drawn strong Western criticism, with renewed anger from Washington and London over the additional charge for Suu Kyi. Although China has taken a softer line, its ambassador in Myanmar on Tuesday dismissed accusations it supported the coup.

UN Special Rapporteur Tom Andrews said he feared the possibility of violence against the protesters and made an urgent call on any country with influence over the generals, and businesses, to press them to avoid it.

"Continued repression of the people of Myanmar's basic liberties and human rights must end immediately," Andrews said in a statement.

In Yangon and elsewhere, motorists responded to a "broken-down car campaign" spreading on social media, stopping their supposedly stalled cars, with bonnets raised, on streets and bridges to block them to police and military trucks.

Hundreds of people have been rounded up by the army, many of them in night-time raids. Those arrested include much of the NLD's senior leadership.

Myanmar's Assistance Association for Political Prisoners group said more than 450 arrests had been made since the coup.

The military said its takeover and declaration of a state of emergency was in line with the constitution that paved the way for democratic reforms.

"Our objective is to hold an election and hand power to the winning party," Brigadier General Zaw Min Tun, spokesman for the ruling council, told the junta's first news conference since overthrowing Suu Kyi's government.

He said the army would not be in power for long.

The United States was "disturbed" by reports of the additional criminal charge against Suu Kyi, State Department spokesman Ned Price said. Washington imposed new sanctions last week on the Myanmar military.

British Prime Minister Boris Johnson also decried the new criminal charge, saying it was "fabricated" by the military.

As well as the demonstrations in towns across the ethnically diverse country, a civil disobedience movement has brought strikes that are crippling many functions of government.

During protests police have opened fire several times, mostly with rubber bullets, to disperse protesters. A protester who was shot in the head in Naypyitaw last week is not expected to survive.

Australian Associated Press