Britain has criticised "bullying" by the Myanmar junta after the country's ambassador to London was ousted in an extraordinary diplomatic coup after calling for the release of civilian leader Aung San Suu Kyi. 

Diplomats loyal to the Myanmar military authorities seized control of the embassy yesterday, leaving ambassador Kyaw Zwar Minn locked out in the street. 

The ambassador said the defence attache had taken over the mission in "a kind of coup", two months after the military seized power in Myanmar. 

Daily protests demanding a return of democracy have rocked the country and brought a brutal response from the armed forces, with almost 600 civilians killed according to a local monitoring group. 

The coup prompted several high-profile diplomatic defections, including the country's ambassador to the United Nations. 

The junta recalled Kyaw Zwar Minn last month after he issued a statement urging them to release Suu Kyi and deposed civilian President Win Myint.

British foreign minister Dominic Raab tweeted his support for the ambassador, who spent the night in his car outside the embassy. 

"We condemn the bullying actions of the Myanmar military regime in London yesterday, and I pay tribute to Kyaw Zwar Minn for his courage," Mr Raab wrote.

"The UK continues to call for an end to the coup and the appalling violence, and a swift restoration of democracy." 

UK sources said the Myanmar authorities had given official notice of Kyaw Zwar Minn's termination as ambassador, and in line with diplomatic policy the government had no choice but to accept it. 

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Protesters gathered outside the mission yesterday evening with the ousted ambassador, who told the Daily Telegraph that "when I left the embassy, they stormed inside the embassy and took it." 

Asked who had taken over, he replied: "Defence attache, they occupy my embassy". 

According to The Times newspaper, the ambassador said the defence attache had sought to install his former deputy as charge d'affaires. 

Myanmar's security forces have struggled to quell protests and a civil disobedience movement aimed at overturning the 1 February military coup. 

They have used rubber bullets and live rounds to break up rallies and used night raids to arrest suspected dissidents. 

The Assistance Association for Political Prisoners (AAPP) says at least 598 civilians have been killed and nearly 2,900 detained. 

AAPP said that 12 people were killed yesterday.

Local media reports said there were a further 11 deaths today, although this has not been independently verified. 

As part of its efforts to suppress the movement, the junta has issued a wanted notice for some 120 celebrities accused of fanning the protests by lending their support. 

International powers have voiced anger and dismay at the junta's brutal approach, but the UN Security Council has stopped short of considering sanctions, with both China and Russia against the move. 

A group representing the ousted civilian government began talks with UN investigators, saying it had gathered more than 270,000 pieces of evidence showing rights abuses by the junta. 

A lawyer for the Committee for Representing Pyidaungsu Hluttaw (CRPH) - a group of MPs from Ms Suu Kyi's National League for Democracy (NLD) party - met the investigators to discuss alleged atrocities. 

The CRPH says it has evidence of more than 540 extrajudicial executions and 10 deaths of prisoners in custody as well as torture and illegal detentions. 

The military has defended seizing power, pointing to allegations of voting fraud in the November election which Ms Suu Kyi's party won comfortably, and says it is responding proportionately to the demonstrations. 

Junta chief General Min Aung Hlaing accused the protesters of wanting to "destroy the country" and said only 248 protesters had been killed, along with 16 police officers.