The quake caused serious damage to a number of towns and villages but did not seem to have hit heavily populated areas.
The worst hit towns were believed to be Accumoli, Amatrice, Posta and Arquata del Tronto, spokesman for the Italian fire department Luca Cari told Reuters.
Helicopters would be sent up at first light to assess the damage, he said.
The mayor of Accumoli said a number of buildings had been badly damaged.
“Four people are under the rubble, but they are not showing any sign of life. Two parents and two children,” Mayor Stefano Petrucci told Italian RAI television.
RAI quoted police as saying two people were known to have died in the nearby village of Pescara del Tronto.
The mayor of the small town of Amatrice reported extensive damage.
“Half the town is gone,” Sergio Pirozzi told RAI. “There are people under the rubble… There’s been a landslide and a bridge might collapse.”
The earthquake caused damage to towns in three regions – Umbria, Lazio and Marche.
The US Geological Survey, which measured the quake at 6.2 magnitude, said it struck near the Umbrian city of Norcia, which has a picturesque historic centre and is a popular tourist site.
Mayor Nicola Alemanno said no deaths have been reported in Norcia.
“The anti-seismic structures of the town have held. There is damage to the historic heritage and buildings, but we do not have any serious injuries,” he told Rai.
Italy’s Prime Minister Matteo Renzi’s office said rescue teams were being sent to the worst-hit areas.
Italy’s civil protection agency said the earthquake was “severe”.
Local television stations showed images of rubble-strewn streets in a number of towns. The facades of some old stone buildings had collapsed, leaving the inside rooms exposed.
Residents of Rome, 170km from the epicentre, were woken by the quake, which rattled furniture and swayed lights in most of central Italy.
There were 17 reported aftershocks in the three hours following the initial quake, the strongest measuring 5.5, the Italian seismic office said. It measured the original quake at 6.0.
The last major earthquake to hit Italy struck the central city of L’Aquila in 2009, killing more than 300 people.