Residents scoured collapsed buildings Sunday searching for survivors as aftershocks rattled the devastated city of Mandalay, two days after a massive earthquake killed at least 1,700 people in Myanmar and at least 18 in neighbouring Thailand.

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

The tremors collapsed buildings, downed bridges and buckled roads, with mass destruction seen in the city of more than 1.7 million people.

Tea shop owner Win Lwin picked his way through the remains of a collapsed restaurant on a main road in his neighbourhood early on Sunday, tossing bricks aside one by one.

"About seven people died here" when the quake struck, he told AFP. 

"I'm looking for more bodies but I know there cannot be any survivors."

A small aftershock struck in the morning, sending people scurrying out of a hotel for safety, following a similar tremor felt late Saturday evening.

And around 2:00 PM (0730 GMT), another aftershock of 5.1-magnitude according to the US Geological Survey — sent people into the streets in alarm once again, temporarily halting rescue work.

Myanmar's ruling junta said in a statement Sunday afternoon that about 1,700 people were confirmed dead so far, about 3,400 injured and around 300 more missing.

But with communications down in many areas, the true scale of the disaster remains unclear in the isolated military-ruled state, and the toll is expected to rise significantly.

At a destroyed Buddhist examination hall in Mandalay, Myanmar and Chinese responders worked to find buried victims on Sunday.

San Nwe Aye, sister of a 46-year-old monk missing in the collapsed hall, appeared in deep distress, and told AFP she has heard no news about his status.

"I want to hear the sound of him preaching," she said. "The whole village looked up to him."

At a collapsed apartment block in the city, rescuers thought they had saved the life of a pregnant woman trapped under rubble for more than 55 hours.

They even amputated her leg to free her, but after pulling her out they were unable to resuscitate her and she was pronounced dead. 

Myriad challenges

Junta chief Min Aung Hlaing issued an exceptionally rare appeal for international aid on Friday, indicating the severity of the calamity.

Previous military governments have shunned foreign assistance, even after major natural disasters.

Myanmar has already been ravaged by four years of civil war sparked by a military coup in 2021.

Reports have emerged of sporadic violence even after the quake, with one rebel group telling AFP on Sunday that seven of its fighters were killed in an aerial attack soon after the tremors hit.

Anti-junta fighters in the country have declared a two-week partial ceasefire in quake-affected regions starting Sunday, the shadow "National Unity Government" said in a statement.

The UN said overnight that a severe lack of medical equipment is hindering Myanmar's response to the quake, while aid agencies have warned that the country is unprepared to deal with a disaster of this magnitude.

The International Federation of Red Cross and Red Crescent Societies on Sunday launched an emergency appeal for more than $100 million to help victims.

Some 3.5 million people were displaced by the raging civil war, many at risk of hunger, even before the quake struck.

Rescue teams and aid have been arriving from donor countries around the world, with Thailand on Sunday dispatching 55 military personnel and six rescue dogs, along with equipment including cranes and diggers.

Bangkok building collapse

Across the border in Thailand, rescuers in Bangkok worked on Sunday to pluck out survivors trapped when a 30-story skyscraper under construction collapsed after the Friday earthquake.

At least 18 people have been killed in the Thai capital, city authorities said late Sunday afternoon, with 33 injured and 78 still missing.

Most of the deaths were workers killed in the tower collapse, while most of the missing are believed to be trapped under the immense pile of debris where the skyscraper once stood.

The shock of the moment made 22-year-old survivor, Burmese worker Kyaw Lin Htet, feel like he "lost consciousness".

"I never expected this would happen to me as we only see this on TV," he told AFP at the site on Sunday.

Sniffer dogs and thermal imaging drones have also been deployed to seek signs of life in the collapsed building, close to the Chatuchak weekend market popular among tourists.

Authorities said engineers would be assessing and repairing the 165 damaged buildings around the city on Sunday.