The medieval basilica erected in St Benedict's name was almost completely destroyed. Photo: EPA

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 the north.

The 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."

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.

The US Geological Survey said the epicentre of the quake was 68km south-east of the regional centre of Perugia and close to the small town of Norcia, which is believed to be the birthplace of St Benedict.

Images from the town show the almost complete destruction of the medieval basilica erected in St Benedict's name, with just its facade left standing.

"It was like a bomb went off," said the town's deputy mayor, Pierluigi Altavilla.

"We are starting to despair. There are too many quakes now, we can't bear it anymore."