UN Secretary-General Antonio Guterres on Thursday called for more international funding and rapid and unimpeded humanitarian access to Myanmar, as the country continues rescue and reconstruction after a powerful earthquake caused massive casualties and widespread destruction.

"Myanmar today is the scene of utter devastation and desperation," Guterres said at a press conference. "This disaster has laid bare the deeper vulnerabilities facing people throughout the country."

Even before the earthquake, Myanmar was beset by political and humanitarian crises, he said, adding that the earthquake has supercharged the suffering of the people, with the monsoon season just around the corner.

The UN chief appealed to the international community to immediately step up vitally needed funding to match the scale of the crisis, and called for rapid, safe, sustained and unimpeded humanitarian access to reach those most in need across the country.

He welcomed the announcements of temporary ceasefires from Myanmar's authorities, and called the move "essential to help aid flow and let rescuers do their jobs."

Guterres said he is sending Emergency Relief Coordinator Tom Fletcher to Myanmar. And Julie Bishop, the UN secretary-general's special envoy for Myanmar, will visit the country in the coming days to reinforce efforts for peace and dialogue.

"The United Nations will keep pushing for peace and lifesaving support for the people of Myanmar in their hour of need," he said.

The death toll from last week's 7.9-magnitude earthquake in Myanmar rose to 3,145 on Thursday, with 4,589 people injured and 221 missing, the Myanmar Radio and Television reported.