A powerful earthquake tore through central Italy on Monday devastating mountain towns and killing at least 27 people, authorities said.
Emergency services scrambled to find victims trapped under thousands of collapsed homes and buildings and warned the toll would rise significantly.
Prime Minister Silvio Berlusconi said he had declared a state of emergency.
L'Aquila, capital of Abruzzo region, about 100 kilometers (60 miles) north of Rome, bore the brunt of the quake which struck just after 3:30 am (0130 GMT).
Sirens blared across the city as rescue workers raced to find people in the rubble. Thousands of the city's 60,000 residents fled into the streets fearing aftershocks.
Hundreds, some in shock and others sobbing, waited outside L'Aquila's main hospital for treatment, ANSA news agency reported. Doctors treated people in the open air as only one operating room was functioning, the agency said.
The city's university hospital was declared off limits for fear it would collapse and the worst victims were being taken by helicopter to other cities.
Police gave a provisional death toll of 20, which included five children in L'Aquila and other towns in the Apennine mountains that run down central Italy, ANSA said.
Guido Bertolaso, head of Italy's public safety department, said there would be "numerous victims, many injured and so many collapsed homes," ANSA reported.
"It's an event that will mobilise the nation for many weeks," he said, adding that at least 10,000 homes or buildings were damaged in the quake.
Roofs fell in on many houses in the region and boulders blocked several mountain roads.
Residents said the shock lasted 20-30 seconds.
Matthew Peacock, who lives with his wife and child in the Umbrian town of Amelia told Britain's Sky television: "It felt like the house was being shaken from the rooftop -- my bed was banging against the wall and you could hear this creaking.
"I rushed across the hallway to my son, who's five, grabbed him and stood underneath the doorway. The shaking went on for 20 seconds or so."
He went on: "The earth really felt like jelly underneath. Dogs outside were making an incredible racket."
Another Briton living in Monte San Marino, a small town in the Apennine mountain range 60 miles to the north east of L'Aquila - said he also woke up to find the house shaking.
Barry Raven told Sky News: "It continued to shake for about 30 seconds.
"When you felt it you were thinking 'Is this the beginning or is this the end?'
Eight people died in L'Aquila, five in Castelnuovo, one in Poggio Picenze, one in Tormintarte and two in Fossa including a three-year-old girl, one in Totani and two in Villa Sant'Angelo, said police quoted by ANSA.
One of the deaths in L'Aquila was a student killed in the collapse of a dormitory, ANSA said.
The epicentre of the quake, which was also felt in Rome, was some five kilometres (three miles) below L'Aquila, public safety officials said, adding that the national geophysical institute had estimated the size at magnitude 5.8.
Some 15,000 people suffered a power outage and part of the highway linking L'Aquila to Rome was closed.
The quake came about five hours after a 4.6-magnitude tremor shook Italy's north-central region with no reports of damage.
That quake occurred at Ravenna in the Emilia-Romagna region about 28 kilometres below ground and was felt over a wide area, notably in the Marche region on the Adriatic coast, public safety officials said.
A powerful earthquake in the region claimed 13 lives in 1997 and damaged or destroyed priceless cultural heritage.
Italy is criss-crossed by two fault lines, with some 20 million people at risk from earthquakes.
An October 2002 quake killed 30 people including 27 pupils and their teacher who were crushed under their schoolhouse in the tiny medieval village of San Giuliano di Puglia.
On November 23, 1980, a violent quake struck the southern region of Irpiona near Naples, killing 2,570, injuring 8,850 and displacing 30,000.