With 368 people injured and an unknown number trapped under rubble, the figure of dead and wounded was expected to rise in the wake of the pre-dawn quake, Prime Minister Matteo Renzi warned.
"This is not a final toll," he said.
Hundreds of people were to spend a chilly night in hastily-assembled tents with the risk of aftershocks making it far too risky for them to return home.
Scores of buildings were reduced to dusty piles of masonry in communities close to the epicentre of the quake, which had a magnitude of between 6.0 and 6.2.
It hit a remote area straddling Umbria, Marche and Lazio at a time of year when second home owners and other visitors swell the numbers staying there. Many of the victims were from Rome.
The devastated area is just north of L'Aquila, the city where some 300 people died in another quake in 2009.
More than half of the deaths occurred in and around the villages of Amatrice, Accumoli and Arquata del Tronto.
Guido Bordo, 69, lost his sister and her husband after they were trapped inside their holiday house in the hamlet of Illica, near Accumoli.
"There's no sound from them, we only heard their cats," he told AFP before the deaths were confirmed.
"I wasn't here. As soon as the quake happened, I rushed here. They managed to pull my sister's children out, they're in hospital now," he added, wringing his hands in anguish.
Sergio Camosi escaped in his underwear with his wife and daughter just before his house caved in.
"We ran down the stairs but the door was blocked by stones so we had to climb out the window," he said tearfully.
Among the victims was a nine-month-old baby girl whose parents survived, an 18-month-old toddler and two other young children who died with their parents in Accumoli.
Two boys aged four and seven were saved by their quick-thinking grandmother, who ushered them under a bed as soon as the shaking began, according to reports. She also survived but lost her husband.
And there were sobs in Illica when two sisters were reunited with their poodle, Lello, pulled alive from their abandoned house.
It was Italy's most powerful earthquake since the 2009 disaster in L'Aquila.
"Half the village has disappeared," said Amatrice mayor Sergio Pirozzi, surveying a town centre that looked as if had been subjected to a bombing raid.
Pope Francis interrupted his weekly audience in St Peter's Square to express his shock.
"To hear the mayor of Amatrice say his village no longer exists and knowing that there are children among the victims, is very upsetting for me," he said.
Civil Protection chief Fabrizio Curcio classed the quake as "severe". The shocks were strong enough to be felt 150 kilometres (90 miles) away in Rome, where authorities ordered structural tests on the Colosseum.
Some of the worst damage was suffered in Pescara del Tronto, a hamlet near Arquata in the Marche region where the bodies of the dead were laid out in a children's play park.
With residents advised not to go back into their homes, temporary campsites were being established in Amatrice and Accumoli as authorities looked to find emergency accommodation for more than 2,000 people.
Amatrice is a hilltop beauty spot famed as the home of amatriciana, one of Italy's favourite pasta sauces, and is a popular destination for Romans seeking cool mountain air at the height of the summer.
It was packed with visitors when the quake struck at 3:36am (0136 GMT).
Three minutes later the clock on the village's 13th-century tower stopped.
The first quake measured 6.2, according to the United States Geological Survey (USGS), which said it occurred at a shallow depth of 10 kilometres (six miles).
It measured 6.0 according to Italian monitors, who put the depth at only four km. A 5.4-magnitude aftershock followed an hour later.
Italy is often shaken by earthquakes, usually centred on the mountainous spine of the boot-shaped country.
In 2009, a 6.3-magnitude earthquake struck close to the university city of L'Aquila in the Abruzzo region and left more than 300 people dead.
That disaster led to lengthy recriminations over lax building controls and the failure of authorities to warn residents that a quake could be imminent.
David Rothery, Professor of Planetary Geosciences at Britain's Open University, said Wednesday's quake had been similar to the 2009 one.
"Both occurred at a shallow depth, which exacerbates the shaking at the surface," he said.
"Unlike the L'Aquila quake, which was preceded by swarms of smaller quakes and led to claims -- unjustified in my view -- that the eventual big quake should have been predicted, this one appears to have struck out of the blue."
Last Updated 31, Mar 2018, 6:37 PM