Nearly 5000 rescue workers are now involved in the search for survivors of the earthquake in central Italy.
The death toll has risen to at least 250, and rescue workers are facing an added danger from aftershocks.
The 6.2 magnitude quake struck a cluster of mountain communities 140km east of Rome early on Wednesday (local time) as people slept, destroying hundreds of homes.
Officials said they expected to confirm more deaths as the search operation continued. Trucks full of rubble left the area every few minutes, including one in which a dusty doll could be seen lying on top of tonnes of debris.
On Thursday, the sun rose on frightened people who had slept in cars or tents, the earth continuing to tremble under their feet from aftershocks, hundreds of which have struck since the quake. Two registered 5.1 and 5.4, just before dawn.
On Thursday afternoon a violent aftershock measuring magnitude 4.3 sent rescuers fleeing from debris and stones that fell from the severely damaged bell tower of the 15th century church of St. Augustine in Amatrice.
The aftershock, which struck fear and panic in survivors, detached the church's facade, leaving it dangerously unstable over the main street where rescuers work.
The original earthquake was powerful enough to be felt in Bologna to the north and Naples to the south, both more than 220 km from the epicentre.
Many of those killed or injured were holidaymakers in the four worst-hit towns - Amatrice, Pescara del Tronto, Arquata del Tronto and Accumoli - where seasonal visitors swell populations by up to tenfold the summer. That makes it harder to track the deaths.
One Spaniard, five Romanians, and a number of other foreigners, some of them care-givers for the elderly, were believed to be among the dead, officials said.
Aerial video taken by drones showed swathes of Amatrice, last year voted one of Italy's most beautiful historic towns, completely flattened. The town, known across Italy and beyond for a local pasta dish, had been filling up for the 50th edition of a popular food festival this weekend.
The mayor said the bodies of 15-20 tourists were believed to be under the rubble of the town's Hotel Roma, which he said had about 32 guests when it collapsed on Wednesday morning.
About 270 people injured in Wednesday's quake were hospitalised, the Civil Protection department said, adding that about 5,000 people, including police, firefighters, army troops and volunteers, were involved in post-quake operations.
Rescuers working with emergency lighting in the darkness saved a 10-year-old girl, pulling her alive from the rubble where she had lain for about 15 hours.
Many other children were not so lucky. A family of four, including two boys aged 8 months and 9 years, were buried when a church bell tower toppled into their house in nearby Accumoli.
Prime Minister Matteo Renzi's cabinet was meeting on Thursday to decide emergency measures to help the affected communities.
"Today is a day for tears, tomorrow we can talk of reconstruction," he told reporters late on Wednesday.
The death toll appeared likely to rival or surpass that from the last major earthquake to strike Italy, which killed more than 300 people in the central city of L'Aquila in 2009.
Most of the damage was in the Lazio and Marche regions, with Lazio bearing the brunt of the devastation and the biggest toll. Neighbouring Umbria was also affected.
Italy's most deadly earthquake since the start of the 20th century came in 1908, when an earthquake followed by a tsunami killed an estimated 80,000 people in the southern regions of Reggio Calabria and Sicily.