More than 15,000 people were staying in hotels and temporary accommodation in central Italy on Monday after the fiercest earthquake in a quarter of a century struck regions already rocked by repeated tremors in the past two months.



No deaths or critical injuries have been reported after Sunday's 6.6 magnitude quake, partly because many had fled their homes after a slightly smaller quake nearby killed almost 300 people in August.



Aerial video footage released by the fire department showed long cracks running through the surface of Redentore Mountain near the epicenter close to the Umbrian walled town of Norcia.



Italy's civil protection authority said more than 4,500 people had been moved to hotels on the Adriatic Coast and around Lake Trasimeno, close to the university city of Perugia.



A further 10,000 had been put up in emergency centers in the Umbria and Marche regions, the authority said, adding to thousands already forced out of their homes by August's quake.



Prime Minister Matteo Renzi pledged to rebuild the stricken areas and make sure corruption did not worm its way into the reconstruction projects.



"Not one cent will be wasted, and we must show that we know how to do public works without waste and without thievery, unlike some episodes in the past," Renzi wrote in a newsletter.



In Norcia, firefighters inspected the damage around the 13th century Basilica of St. Benedict, which collapsed leaving only its facade standing, and the Cathedral of Santa Maria Argentea, whose belltower was severely cracked.



"We will try to rescue all the cultural heritage that has survived but we are right in the center of seismic activity, the tremors are very, very intense," fireman Domenico De Vita said.



Sunday's tremor was felt as far north as Bolzano, near the Austrian border, and in the southernmost region of Puglia.



Schools were closed on Monday in the capital Rome, whose mayor Virginia Raggi said checks were being carried out on buildings and the city's evacuation plan was being updated.



"Every crack, every fault that might emerge will be checked," she said. "We cannot delay any more."



Leading seismologist Gianluca Valensise warned on Sunday the earthquakes could go on for weeks in a domino effect along the central Apennine fault system.