Gianfranco Fini, speaker of the lower house of parliament, told MPs: "Some towns in the area have been virtually destroyed in their entirety."
Such is the damage in L'Aquila, where between 3,000 and 10,000 buildings were reportedly affected, that the city will be uninhabitable for some time, the BBC's David Willey reports.
Surrounding villages were also hit hard:
In the village of Onna, 24 people were killed, according to the Italian news agency Ansa; the village of 250 was virtually deserted as survivors sought shelter
In Castelnuovo, a village of about 300 people, five deaths were confirmed
It has been reported that a major earthquake in the L'Aquila area was predicted by an Italian scientist several weeks ago.
But a spokesman for the Italian Civil Protection Agency, Dr Agostino Miozzo, was adamant that this was not possible.
"We can only say that an area is prone to earthquakes," he told the BBC.
"From here down to Sicily is historically an area interspersed by earthquakes, but even that we cannot predict."
Fire-fighters aided by dogs worked feverishly to reach people trapped in fallen buildings in L'Aquila, including a student dormitory where several students were believed to be still inside.
AT THE SCENE
Duncan Kennedy, BBC News, L'Aquila
Here in the centre of the city, building after building has been left destroyed or half standing with cracks and holes.
We watched as rescue workers struggled to pull out survivors, crawling on their stomachs to try to reach those trapped inside.
There is a stream of almost ghostly figures, local people caught up in the early hours this morning in this earthquake, who are pouring past us wearing blankets.
They are pulling suitcases and luggage past this collapsed building trying to get to safety. People are wandering around in a dazed state.
Residents and rescuers used their bare hands to clear the debris from collapsed buildings.
"We are not using machines for this because experience has shown us that it is important to dig by hand [to avoid further casualties]," said Mr Berlusconi after arriving in L'Aquila.
He said a field hospital, 2,000 tents and 4,000 hotel rooms were being made available.
"I can assure you that there is no building that has fallen down without rescuers, without fire brigade being there," he told reporters.
Italy, he said, had the resources it needed to deal with the disaster: "Financially, there are no problems. The government has all the necessary funds at its disposal. We also have the EU catastrophe fund."
Officials say 26 cities and towns have been damaged in the region, not including villages and hamlets.
There have been stories of rescues all day, the BBC's Duncan Kennedy reports from L'Aquila.
Men, women and children have been brought out of the rubble, some carried on ladders used as makeshift stretchers, some screaming with delight at having survived.
'Struck the heart'
The 6.3-magnitude quake struck at 0330 (0130 GMT) close to L'Aquila, 95km (60 miles) north-east of Rome.
Medieval city, founded in the 13th Century
Capital of the mountainous Abruzzo region
Population 70,000, with many thousands more tourists and foreign students
Walled city with narrow streets, lined by Baroque and Renaissance buildings
It lasted about 30 seconds, bringing down many Renaissance-era and Baroque buildings, including the dome on one of L'Aquila's churches.
Boulders fell off mountain slopes, blocking roads. Houses were reduced to piles of rubble and cars crushed by raining debris.
One resident, Antonio di Marco, recounted his experience for the BBC: "We escaped outside like madmen, we didn't understand what was happening, the whole building was moving under our feet, it is something that's impossible to describe "
"It's a catastrophe and an immense shock," resident Renato Di Stefano told the Associated Press as he and his family headed for shelter in a tent camp outside L'Aquila.
"It's struck in the heart of the city, we will never forget the pain."
'State of shock'
Dr Miozzo said many survivors faced a rough night ahead.
Quake homeless arrive at 'tent city'
"Tonight we'll have a great number of people that will sleep in their car, people that will go to their relatives in the neighbouring area, in the neighbouring towns that are in safe conditions," he told the BBC.
"But they are very shocked, you see, especially the aged people and obviously children."
Phone and power lines have been down and some bridges and roads have been closed as a precaution against aftershocks.
Italy lies on two fault lines and has been hit by powerful earthquakes in the past, mainly in the south of the country.
MAJOR ITALIAN QUAKES
2002 - 30 die, including 27 pupils and their teacher, in the southern town of San Giuliano di Puglia
1997 - 13 die and priceless cultural heritage lost in the central Umbria region
1980 - Nearly 3,000 people die, some 9,000 injured and 30,000 displaced near Naples
World leaders have sent messages of condolence and Pope Benedict XVI offered prayers for the "victims, especially the children".
The EU, Austria, France, Germany, Greece, Israel and Russia immediately stepped forward with offers of aid, if required.
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