International rescue teams and aid are pouring into Myanmar as the death toll from a powerful earthquake continues to rise and fears mount over critical shortages of food, electricity and water.

The magnitude-7.9 quake, among the most powerful to hit Myanmar in the past century, struck on Friday, leaving around 1,700 people dead, 3,400 injured and over 300 unaccounted for as of Sunday.

Senior General Min Aung Hlaing, chairman of Myanmar's State Administration Council, cautioned that the death toll could climb, state media reported, three days after he made an unusual appeal for international aid.

China, India and Thailand are among those sending relief materials and rescue teams into the affected areas. Malaysia, Singapore and Russia also sent aid and personnel.

Read more: China sends first batch of aid to earthquake-hit Myanmar

International rescuers have been racing against time in their search for survivors. On Monday morning, Chinese rescuers freed a child who had been trapped for about 60 hours from under the rubble of the collapsed Sky Villa Condominium in Mandalay. The child was the fourth person recovered by Chinese rescue workers in Myanmar, according to China Media Group (CMG).

Relief efforts, however, have been hampered as key infrastructure, including bridges, highways, airports and railways, has suffered extensive damage across the nation. Residents in the affected cities of Mandalay and Sagaing said international aid had yet to reach them, according to Reuters.

About 80 percent of buildings and homes in Sagaing suffered from varying degrees of destruction, many of which have completely collapsed, CMG reported. Local residents were facing immense difficulties, lacking clothing, food, clean drinking water and medical supplies, while rescue efforts relied solely on local authorities and spontaneous efforts by the public, it said.

"The destruction has been extensive, and humanitarian needs are growing by the hour," the International Federation of Red Cross and Red Crescent Societies (IFRC) said in a statement.

The IFRC has launched an emergency appeal for 100 million CHF ($113.60 million) to assist 100,000 people with life-saving relief and early recovery support.

On Sunday, the World Health Organization declared the Myanmar earthquake a top-level emergency, urgently requesting $8 million to save lives and prevent disease outbreaks in the next 30 days.

It warned that the large number of casualties and trauma victims were highly vulnerable to infections, due to Myanmar's limited surgical capabilities, and that the already challenging conditions in the country of some 50 million could further exacerbate the risk of disease following the disaster.

In neighboring Thailand, parts of which were also shaken by Friday's quake, 18 people died and 78 remained missing.

Local authorities reported damage to buildings in 18 provinces across the country, but the situation has been kept under control, with the risk of aftershocks gradually diminishing, the Department of Disaster Prevention and Mitigation said on Sunday.