The death toll from a huge earthquake that hit Myanmar and Thailand passed 1,000 on Saturday, as rescuers dug through the rubble of collapsed buildings in a desperate search for survivors.

In the early afternoon, a shallow 7.7-magnitude quake struck northwest of the city of Sagaing in central Myanmar, followed minutes later by a 6.7-magnitude aftershock.

The quake destroyed buildings, downed bridges, and buckled roads across swathes of Myanmar, with massive destruction seen in Mandalay, the country's second biggest city and home to more than 1.7 million people.

At least 1,002 people were killed and nearly 2,400 injured in Myanmar, the ruling junta said in a statement.