The death toll from the massive earthquake that razed three towns in central Italy stood at 250 on Thursday, but authorities said they expect the count to rise significantly.
Speaking at a press conference in Rome, Immacolata Postiglione, head of the emergency department at the country's civil defence agency, Protezione Civile, said there were 365 people in hospital.
The magnitude-6 quake struck a mountainous area between the regions of Umbria, Lazio and Marche at 3:36 am (0136 GMT) on Wednesday, toppling buildings and leaving many people trapped under the rubble in the municipalities of Amatrice, Accumoli and Arquata del Tronto.
Rescue efforts have been complicated by hundreds of aftershocks, with strong 4.3-magnitude temblor rattling affected areas on Thursday.
In an interview with the SkyTG24 news channel, Protezione Civile director Fabrizio Curcio said the number of victims could be "worse than the one in L'Aquila," a town where an earthquake killed 309 in 2009.
Many of the victims were children.
In Amatrice, an 11-year-old boy could be heard crying for help on Wednesday, but when rescuers managed to get to him hours later, he was dead.
The remote hilltop towns in the earthquake area are a typical holiday destination for former residents returning to visit grandparents or other relatives, or for city dwellers taking a break from the summer heat.
Foreigners also lost their lives. Five Romanians were confirmed dead by the Foreign Ministry in Bucharest. A spokesman for the Spanish Foreign Ministry also confirmed to dpa that a Spanish national was among the victims. Local media said she was a 27-year-old woman.
Prefect Bruno Frattasi, speaking for the fire services, said 215 people had been rescued alive from the rubble. Postiglione said more may have been saved by other police forces involved in search efforts, but data was not yet available.
Emergency rescue staff are committed to working until they "are sure that there are no more people under the ruins," Luigi D'Angelo, a civil protection official in Amatrice, told public broadcaster Rai News 24.
"We are in a phase where we can still hope to find people alive," a spokesman for the fire service, Luca Cari, told private broadcaster SkyTG 24. He recalled that, in the L'Aquila quake, which had a similar magnitude, one person was rescued after 72 hours.
Protezione Civile said 6,000 rescue workers were in the affected area. It also appealed for people to stop sending food and clothing, as it already has enough on hand. It warned people against travelling to the area, either as tourists or as volunteers in the rescue effort.
If anything, the head of the Protezione Civile said there were too many volunteers in the area.
"I can understand people's solidarity and enthusiasm, but there are too many people in Amatrice, we need tranquillity," Curcio said.
In Amatrice, hundreds of people spent the night in makeshift camp beds inside a local sports hall or in tents put up by authorities on a nearby football pitch. Others preferred to sleep in their cars, ready to leave in case of another major shock.
One focus of the town's fears was the historic Hotel Roma, which was destroyed. It hosted a restaurant famous for Amatriciana pasta, a local delicacy. Mayor Sergio Pirozzi told the Adnkronos news agency the hotel had 35 guests at the time of the shock, lowering a previous estimate of 70.
In Amatrice, bodies could be seen wrapped in blankets and lined up on the grounds of a small park, surrounded by weeping relatives. In Arquata, the quake devastated the cemetery too, unearthing some coffins, the ANSA news agency reported.
At least 293 cultural structures and sites were damaged, including 50 severely, Culture Minister Dario Franceschini said.
The government in Rome declared a state of emergency and pledged 50 million euros (56 million dollars) to go toward aid and reconstruction efforts.
Meanwhile, flags were flying at half-mast at public buildings across Italy as a symbol of national mourning.
Visiting the earthquake zone Wednesday, Prime Minister Matteo Renzi said: "It is a pain without limits."
In depth coverage
Rescue workers raced against time to find survivors from an earthquake that struck central Italy Wednesday, as the death toll reached at least 159.
Italian Prime Minister Matteo Renzi pledges assistance for the quake-hit region of central Italy, where at least 37 people have died.
At least 120 people have died in the severe earthquake in central Italy, Italian Prime Minister Matteo Renzi said Wednesday evening on a visit to the affected region.