Search efforts continued overnight but were hampered by driving rain, as thousands of weary and homeless survivors huddled in tents, cars or makeshift shelters.
Sabina Castelfranco, a Rome-based journalist, told Al Jazeera that people had been up all night, walking around draped in blankets.
Berlusconi said up to 100,000 people may have been made homeless in some 26 cities and towns.
"Tonight, don't go back to your houses, it could be dangerous," he told residents in a message broadcast on state television.
"No one will be abandoned to his fate," he said, adding that a tent village was being set up that could accommodate between 16,000 and 20,000 people.
State of emergency
The prime minister earlier declared a state of emergency after the magnitude 6.3 quake hit the Abruzzo region early on Monday morning.
|Survivors took shelter in tents and cars [AFP]
Berlusconi, who cancelled a trip to Russia in order to visit L'Aquila, a medieval mountain town about 100km northeast of Rome, also pledged an initial 30 million euros ($40m) in immediate assistance.
Police were also patrolling the streets to prevent crime and were 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.
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."
The earthquake also left thousands of houses, churches and buildings damaged or destroyed.
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.
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 and was followed by more than a dozen aftershocks.
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.
Italy lies on two fault lines and has been struck by powerful earthquakes in the past, mainly in the south of the country.