Italy quake: Norcia tremor destroys ancient buildings
Towns and villages in central Italy have been hit by an earthquake for the fourth time in three months.
The 6.6-magnitude quake - Italy's strongest in decades - struck close to the region where nearly 300 people were killed by a quake in August.
This time no-one appears to have died, but about 20 people were injured.
The medieval basilica of St Benedict in Norcia, the town closest to the epicentre, was among buildings destroyed.
An evacuation of buildings in the region deemed vulnerable to seismic activity last week, following strong aftershocks from August's quake, may have saved lives.
Tremors from this latest earthquake were felt in the capital Rome, where the Metro system was shut down, and as far away as Venice in thThe head of the national civil protection agency, Fabrizio Curcio, said there had been extensive damage to many historic buildings but no deaths had been registered.
"About 20 people are injured. As far as people are concerned, the situation is positive, but many buildings are in a critical state in historic centres and there are problems with electricity and water supplies," he added.
Prime Minister Matteo Renzi has promised that everything will be rebuilt, saying resources will be found.
"We are going through a really tough period," he said. "We must not allow the profound pain, fatigue and stress that we have now to turn into resignation."e north.
Pope Francis mentioned the quake in his Sunday blessing in Rome's St Peter's Square.
"I'm praying for the injured and the families who have suffered the most damage, as well as for rescue and first-aid workers," he said to loud applause.
Why multiple quakes are hitting Italy - by Jonathan Amos, BBC science correspondent
We have now seen three magnitude-6 tremors in Italy's Apennines region in just three months.
The big picture is reasonably well understood. Wider tectonic forces in the Earth's crust have led to the Apennines being pulled apart at a rate of roughly 3mm per year - about a 10th of the speed at which your fingernails grow.
But this stress is then spread across a multitude of different faults that cut through the mountains. And this network is fiendishly complicated.
It does now look as though August's event broke two neighbouring faults, starting on one known as the Laga and then jumping across to one called the Vettore.
The mid-week tremors appear to have further broken the northern end of the Vettore. But both in August and mid-week, it seems only the top portions of the faults have gone, and the big question is whether the deeper segments have now failed in the latest event.