Italian prime minister Matteo Renzi has pledged to find temporary housing for all those displaced by a series of powerful earthquakes in a central mountainous region.

The promise comes after the strongest quake to hit Italy in 36 years left more than 15,000 people in need of assistance.

There were no deaths or serious injuries after Sunday morning's 6.6-magnitude tremor, largely because most fragile city centres had already been closed because of previous damage and many homes had been vacated.

However, it did complicate quake relief efforts in a zone which is still coping with the aftermath of an August quake which killed nearly 300 in the same region around the Apennine Mountains, and a pair of powerful aftershocks last week which also claimed no lives.

Civil protection officials expect the number of people needing assistance to continue to rise, as it does not count the many people who slept in vehicles or made other arrangements and are likely to seek help.

Temperatures overnight reached near freezing, and officials have expressed concern for the many elderly residents of the mountain communities.

"We cannot have tents for some months in the mountains, under the snow," Mr Renzi said.

"There are enough hotels for everyone. But many of our compatriots don't want to leave their lands, not even for some weeks."

Many people have been moved to coastal areas, where summer resort hotels are mostly idle, and other zones away from the quake.

There are increasing reports of residents resisting in the belief that if their homes have so far resisted, that they remain the safest place to be.

In the town of Norcia, closest to the epicentre, firefighters were taking people back to their homes to retrieve belongings.

They were given helmets as protection, and taken in in small groups as they arrived. The ground continued to shake overnight with at least two jolts above magnitude four.

"We were inside our home and luckily the house handled it," said Emanuela Spanicciati, one resident of Norcia.

"And that allowed us to get out into the streets. There were various injured people, but in the end we were lucky."

Mr Renzi said the fact that there were no deaths "gives us enormous relief. But the damage to the housing stock, as well as economic, cultural and religious treasures is impressive. These villages are the identity of Italy. We must reconstruct them all, quickly and well".

Many of the towns struck are of historic significance, including Norcia, where a Benedictine cathedral collapsed, leaving just a facade.

AP