The earthquake is believed to have left more than 1,500 people injured and thousands of houses, churches and buildings damaged or destroyed.
Berlusconi said up to 100,000 people may have become homeless in some 26 cities and towns.
He said "no one will be abandoned to his fate", and that the shelters being set up could accommodate between 16,000 and 20,000 people.
Police have begun going door to door in L'Aquila, checking that people who had decided to stay in the crippled town, most of them elderly, had what they needed for the night.
"We're also patrolling to prevent thefts from empty homes," an officer told the AFP news agency after reports of looting.
Angela Palumbo, 87, a resident of L'Aquila, said: "I woke up hearing what sounded like a bomb. We managed to escape with things falling all around us.
"Everything was shaking, furniture falling. I don't remember ever seeing anything like this in my life."
Part of a university residence and a church tower were among the buildings that had collapsed in L'Aquila, officials said.
Television footage showed rubble blocking streets in the town and burying several parked cars.
"Police are asking people to stay away from buildings, away from lamp-posts, away from anything that could fall," Al Jazeera's Ayman Mohyeldin, reporting from L'Aquila, said.
"Many of these buildings are clearly showing signs of cracks, showing signs of broken windows. Glass is scattered all along the streets.
"There are fears that aftershocks could trigger more collapses and trap more people."
Our correspondent reported, quoting a local government official Ugo DePaolis, that 60 people died in the town of Onna alone, approximately 5km from L'Aquila.
Massimo Cialente, L'Aquila's mayor, told Sky Italia television that about 100,000 people had left their homes and many buildings in the city's historic centre were damaged.
"The civil defence department is setting up some sort of tent town where they will be housed until the situation with their homes is made clearer," Sabina Castelfranco, a Rome-based journalist, told Al Jazeera.
"People are walking around draped in blankets, they have been up all night."
Antonio D'Ostilio, a resident of L'Aquila, said: "We left as soon as we felt the first tremors.
"We woke up all of a sudden and we immediately ran downstairs in our pyjamas."
Hundreds of people waited outside the town's main hospital while doctors treated people in the open air since only one operating room was functioning.
The city's university hospital was declared off limits due to concerns that it could collapse.
According to the US Geological Survey, the epicentre of the earthquake was about 95km northeast of Rome, at a depth of about 10km.
It struck at 3:32am local time (01:32 GMT) when many people were asleep.
Italy lies on two fault lines and has been struck by powerful earthquakes in the past, mainly in the south of the country.