"It is absolutely unacceptable to see violence against people at such high levels, so many people killed, and such a stubborn refusal to accept the need to liberate all political prisoners and to make the country go back to a serious democratic transition," Guterres told a news conference.

"We need more unity... (and) more commitment from the international community to put pressure in order to make sure that the situation is reversed," he said.

Since a February 1 coup, soldiers and police have waged a brutal campaign against mass anti-coup protests demanding a restoration of democracy and the release of ousted civilian leader Aung San Suu Kyi.

This past weekend was the deadliest, with at least 107 people, including seven children, killed on Saturday, the United Nations said. A further 13 people were killed on Sunday, according to the Assistance Association for Political Prisoners (AAPP) monitoring group.

Britain has called for an emergency UN Security Council meeting on the situation in Myanmar, according to diplomatic sources.

The 15 Security Council members will begin the session behind closed doors Wednesday with a briefing on the situation by the UN's special envoy on Myanmar, Christine Schraner Burgener, the sources said.