Italy's most powerful earthquake in 36 years has left more than 15,000 people homeless, authorities said Monday as the scale of the damage done to irreplacable historic buildings became apparent.

Although Sunday's 6.6-magnitude tremor did not result in any deaths, the third powerful quake in just over two months has left thousands of homes in ruins or structurally unsafe and emptied a string of villages and small towns across the country's mountainous central regions.

The series of tremors, all followed by powerful aftershocks, proved the final straw for a number of important architectural landmarks, including the Abbey of Sant-Eutizio in Umbria.

With roots dating back to the 5th century, the abbey is one of the oldest monastic sites in Italy and was celebrated for both its 12th century Romanesque facade and its Renaissance belltower.

That rich history was reduced to a pile of ruins on Sunday, leaving local priest Luciano Avenati heartbroken.

"Perhaps we will rebuild but this place will never again be like it was," he told AFP.

"It is an unimaginable loss.

"This whole region is going to find it hard to recover and the generations to come will only know what it once was through pictures of the past."

- Architectural gems destroyed -

The majority of residents of the devastated communities have taken refuge with friends and family as they anxiously await a green light to return to their homes.

But the national civil protection agency said Monday it was providing assistance to 15,000 people affected by Sunday's quake, which was so powerful it caused cracks in buildings in Rome, some 120 kilometres (75 miles) away from the epicentre near the Umbrian town of Norcia.

Some 4,000 people from the worst-hit area around Norcia have been sent to hotels on the Adriatic coast with another 500 taken by bus to the inland Lake Trasimeno.

More than 10,000 are being put up in converted sports halls and other temporary facilities, including tents, across Umbria and the neighbouring Marche region, the agency said.

A further 1,100 people are still in Adriatic coast hotels as a result of the August 24 Amatrice earthquake, which left nearly 300 dead.

Prime Minister Matteo Renzi on Monday said that shipping containers would be brought in as temporary housing.

"Tents are not a solution for December. We will deliver these containers before Christmas, so that people can wait until spring or summer 2017 when we expect to have completed wooden houses for them pending proper reconstruction," he said.

Given the strength of Sunday's new quake, experts said it was remarkable that it had not resulted in any more fatalities.

Other architectural gems destroyed included the 14th century Basilica of St Benedict in Norcia and the 13th century Civic Tower in Amatrice.

A belltower at the sanctuary of Santa Maria in Via in the medieval university town of Camerino was destroyed last week, despite extensive renovation and seismic protection work after a previous quake in 1997.

- 'No future' -

In a statement released late on Monday, the government said it had decided to allocate an immediate 40 million euros ($44 million) to cover the initial costs of the latest quake.

Meanwhile, schools in Rome were closed all day for structural checks and there was traffic chaos in the east of the capital because of the closure of a key flyover for assessment by engineers.

A large crack appeared in the facade of one of Rome's four principal papal churches, the Basilica of St Paul Outside the Walls, and the Mazzini bridge over the river Tiber was also closed for checks.

The quake was Italy's biggest since a 6.9-magnitude one struck the south of the country in 1980, leaving 3,000 people dead.

It has been followed by hundreds of powerful aftershocks feared to have further compromised the safety of buildings in the affected area.

Renzi has vowed that every damaged house will be rebuilt while Culture Minister Dario Frenceschini says every damaged fresco will be pieced back together.

But all that will carry a hefty bill and after the trauma of three major quakes in such quick succession, the future of the affected areas, which are already sparsely populated, looks bleak.

"At the moment I don't see any possible future," evacuated Norcia resident Antonella Ridolfi told AFP.

"We have always bounced back after other earthquakes but we've never had to deal with one as strong as this."