A powerful earthquake with a preliminary magnitude of 6.6 has rocked the same area of central and southern Italy hit by a quake in August and a pair of aftershocks last week.
Thousands of people have been left homeless after a week of quakes and this latest tremor sent already damaged buildings crumbling.
Residents rushed into piazzas and streets after being roused from bed by the quake, at 7.40am local time. But there were no immediate reports of injuries or deaths.
Many people had still been sleeping in cars after a pair of strong jolts last Wednesday. Others had been evacuated to shelters or hotels in other areas.
Television images showed nuns rushing out of their church and into the main piazza in Norcia as the clock tower appeared about to crumble. One had to be carried by firefighters, while another was supported as she walked.
The mayor of quake-hit Ussita said a huge cloud of smoke erupted from the crumbled buildings.
“It’s a disaster, a disaster!” Mayor Marco Rinaldi told the ANSA news agency. “I was sleeping in the car and I saw hell.”
Another hard-hit city, Castelsantangelo sul Nera, also suffered new damage. And in Arquata del Tronto, which had been devastated by the August 24 earthquake that killed nearly 300 people, Arquata Mayor Aleandro Petrucci said: “There are no towns left.”
“Everything came down,” he said.
The quake was felt throughout the Italian peninsula, as far north as Bolzano and as far south as Bari.
In Rome, residents rushed into the streets. Ancient palazzi shook, swayed and lurched for a prolonged spell, and people took to Twitter to share their experiences of the quake.
The head of the civil protection authority in the March region, Cesare Spuri, said there have been reports of buildings collapsing in many cities.
Monks at the monastery of San Benedetto, an international Benedictine community in Norcia, tweeted an image of the Basilica of St Benedict destroyed by the earthquake.
The church had withstood the August earthquake in August and last week’s aftershocks, and was still standing.
But television pictures showed piles of stone had accumulated at the bottom of one wall. One stone was thrown metres into the centre of the piazza, illustrating the quake’s force.
“We have to keep people calm. Prayer can help. I don’t want people to go searching for family members,” a firefighter appealed as cameras from SKY TG24 filmed.