The World Health Organisation (WHO) said on Sunday that the Myanmar earthquake was a top-level emergency as it urgently sought US$8 million to save lives and prevent disease outbreaks over the next 30 days.

The WHO said the high numbers of casualties and trauma injuries were at high risk of infection due to limited surgical capacity in the country, while the underlying conditions in Myanmar meant the quake was likely to intensify the risk of disease.

"WHO has classified this crisis as a Grade 3 emergency - the highest level of activation under its Emergency Response Framework," the United Nations health agency said in its flash appeal for funds.

The initial 7.7-magnitude quake struck near the central Myanmar city of Mandalay on Friday, followed minutes later by a 6.7-magnitude aftershock.

The quake has killed more than 1,700 people in Myanmar and at least 18 in neighbouring Thailand.

In Myanmar, "preliminary assessments indicate high numbers of casualties and trauma-related injuries, with urgent needs for emergency care. Electricity and water supplies remain disrupted, worsening access to health services and heightening risks of waterborne and food-borne disease outbreaks," the WHO said.

"Trauma-related injuries - including fractures, open wounds, and crush syndrome - are at high risk of infection and complications due to limited surgical capacity and inadequate infection prevention and control."

The WHO said hospitals were overwhelmed, while the scale of deaths, injuries and damage to health facilities "are not yet fully understood".

The agency said displacement into overcrowded shelters, combined with the destruction of water systems and sanitation infrastructure, had sharply increased the risk of communicable disease outbreaks. (AFP)