"We have terminated a number of channels and removed several videos from YouTube in accordance with our community guidelines and applicable laws," a YouTube spokeswoman said in a statement.

The channels taken down include the state network, MRTV, (Myanmar Radio and Television) as well as the military-owned Myawaddy Media, MWD Variety and MWD Myanmar, according to the US tech giant.

Pro-democracy activists held more demonstrations in Myanmar on Friday to oppose the February 1 ouster of the elected government of Aung San Suu Kyi.

A big crowd marched peacefully through the city of Mandalay chanting: "The stone age is over, we're not scared because you threaten us".

There was no immediate sign of a police effort to block them.

But in the main city of Yangon, police fired rubber bullets and stun grenades to disperse protesters who had been joined by about 100 doctors in white coats, witnesses said.

A crowd also gathered in the town of Pathein, to the west of Yangon, a witness said.

On Thursday, police broke up rallies with tear gas and gunfire in several cities but their crackdown was more restrained than on the previous day, when the United Nations said 38 people were killed in the bloodiest day of protests.

UN human rights chief Michelle Bachelet demanded the security forces halt what she called their "vicious crackdown on peaceful protesters".

Bachelet said more than 1700 people had been arrested, including 29 journalists.

A clash over who represents Myanmar at the United Nations in New York was averted - for now - after the junta's replacement quit and the Myanmar UN mission confirmed that Ambassador Kyaw Moe Tun remained in the job.

The junta fired Kyaw Moe Tun on Saturday after he urged countries at the UN General Assembly to use "any means necessary" to reverse the coup.

Myanmar activists are calling for the release of Suu Kyi, 75, who was detained on the morning of the coup, and recognition of her November 8 election victory.

They also reject the junta's promise to hold new elections at an unspecified date.

Sources told Reuters that Myanmar's military rulers attempted to move about $US1 billion ($A1.3 billion) held at the Federal Reserve Bank of New York days after seizing power. US officials froze those funds indefinitely, they said.

The US Commerce Department designated trading curbs on Myanmar's Ministry of Defence, Ministry of Home Affairs and two military conglomerates that control swathes of the economy, with interests ranging from beer to real estate.

But the measures are expected to have limited impact as the entities are not major importers.

Australian Associated Press