Rescuers in Afghanistan and Pakistan are struggling to reach earthquake-stricken regions as officials said the combined death toll has risen to 376.
Authorities said 258 people died in Pakistan and 115 in Afghanistan in the magnitude-7.5 quake, which was centred in Afghanistan's sparsely populated Badakhshan province that borders Pakistan, Tajikistan and China. Three people died on the Indian side of the disputed region of Kashmir.
Officials on both sides of the Afghan-Pakistan border warned that casualty figures will likely leap once relief workers return from villages so remote they can only be accessed on foot or by donkey.
The earthquake, with its epicentre close to the Badakhshan district of Jarm, damaged many of the few existing roads, officials said. The Pakistani town closest to the epicentre is Chitral.
Dropping aid by air will be the only way to reach many of the people in need, but those operations are not likely to start for many days until survey teams on foot return and report on the damage.
Monday's quake shook buildings in the capital Islamabad and cities elsewhere in Pakistan and Afghanistan for up to 45 seconds in the early afternoon, creating cracks in walls and causing blackouts.
The earthquake destroyed more than 7,600 homes across Afghanistan and injured 558 people, according to a statement from President Ashraf Ghani's office.
He ordered the military to make assets available for the relief effort.
Badakhshan governor Shah Waliullah Adeeb said more than 1,500 houses there were either destroyed or partially destroyed.
The province's casualty figures of 11 dead and 25 injured "will rise by the end of the day, once the survey teams get to the remote areas and villages", Mr Adeeb said.
Food and other essentials were ready to go, he said, but "getting there is not easy". Many people in stricken areas were sleeping outdoors, braving freezing temperatures for fear of aftershocks.
Afghan authorities said they were scrambling to access the hardest-hit areas near the epicentre, located 73 kilometres (45 miles) south of Fayzabad, the capital of Badakhshan province.
Badakhshan is one of the poorest areas of Afghanistan and frequently hit by floods, snowstorms and mudslides. Its valleys and mountains make access to many areas by road almost impossible at the best of times. It often has big earthquakes, but casualty figures are usually low because it is so sparsely populated, with fewer than one million people.