Many of the dead were in the historic town of Amatrice, where the mayor said three-quarters of the town was destroyed, and in nearby Accumoli.

Many people are still believed to be buried under rubble.

"This is not a final toll," Mr Renzi warned as he gave the latest figures.

He had earlier paid tribute to the volunteers and civil defence officials who had rushed to the scene in the middle of the night and used their bare hands to dig for survivors.

He promised "no family, no city, no hamlet will be left behind".

The tremor was felt across Italy, from Bologna in the north to Naples in the south. There have been dozens of aftershocks.

Hardest hit were the small towns and villages in the mountainous area where the regions of Umbria, Lazio and Le Marche meet.

Italy's civil protection department said that at least 73 people were now known to have been killed.