Italy yesterday declared a day of mourning for victims of a devastating earthquake as hopes of finding any more survivors dwindled and the confirmed death toll rose to 267.

Flags will fly at half-mast across the country today to coincide with funerals for some of the victims.

Immacolata Postiglione, head of the Civil Protection agency's emergency unit, said no new survivors had been found overnight in the remote mountain villages blitzed by Wednesday's powerful pre-dawn quake.

At least 387 people have been hospitalised with injuries but no one has been pulled alive from the piles of collapsed masonry since Wednesday evening.

"We will go on searching and digging until we are certain there is no one left," said Luigi D'Angelo, a local Civil Protection official.

Valerio Checchi, an officer with a forestry police unit, said he expected rescuers to shortly start using bulldozers to clear the debris in a sign virtually all hope of survivors has gone.

"We will still use thermal devices that can detect the presence of human bodies."

Prime Minister Matteo Renzi has declared a state of emergency for the regions affected by Wednesday's quake, which occurred in an area that straddles Umbria, Lazio and Marche.

Renzi also released an initial tranche of 50 million euros ($56 million) in emergency aid.

Some 2,100 people who spent the night in hastily-erected tented villages were shaken by a 4.8 magnitude aftershock just after 6:00 am yesterday morning.

More than 900 aftershocks have rattled the region since Wednesday's 6.0-6.2 magnitude first one triggered the collapse of hundreds of ill-prepared old buildings across dozens of tiny communities playing host to far more people than usual because of the summer holidays.

Many of the survivors camping out in the tents were carrying plastic bags containing the handful of possessions -- clothes, ID documents, phones and wallets -- they had been able to grab before fleeing their homes in terror.

Quake experts have estimated that the cost of the short-term rescue effort and mid- to longer-term reconstruction could exceed one billion euros ($1.13 billion).

At least eight foreigners were among the dead, according to media reports and updates from foreign ministries.

British media, citing an official in Amatrice, said three Britons had died, including a 14-year-old boy.

Renzi's government and local authorities are now facing questions as to why there had been so many deaths in a sparsely-populated area so soon after a 2009 earthquake in the nearby city of L'Aquila left 300 people dead.