An 80-meter section of the bridge, including one set of the supports that tower above it, crashed down in the rain onto the roof of a factory and other buildings, crushing at least one truck and plunging huge slabs of concrete into the river below.

"It's not acceptable that such an important bridge was not built to avoid this kind of collapse," Deputy Transport Minister Edoardo Rixi said on SkyNews24, speaking from Genoa.

He said the collapse had killed at least 22 people but the number of dead would climb.

Helicopter footage on social media showed trucks and cars stranded on either side of the 50-meter high collapsed section of the Morandi Bridge, which was built on the A10 toll motorway in the 1960s. One truck was shown just meter away from the broken end of the bridge.

Restructuring work on the 1.2 km-long bridge, a major artery to the Italian Riviera and to France's southern coast, was carried out in 2016. The highway operator said work to shore up its foundation was being carried out at the time of the collapse, adding that the bridge was constantly monitored.

A witness told Sky Italia television he saw "eight or nine" vehicles on the bridge when it collapsed in what he said was an "apocalyptic scene".

Some 200 firefighters were on the scene, the fire service said, and Italian news agency ANSA said two survivors had been pulled out of the rubble under the collapse.

Police footage showed firemen working to clear debris around a crushed truck, while other fireman nearby scaled broken slabs of the collapsed bridge support.

Transport Minister Danilo Toninelli told Italian state television the disaster showed the dilapidated state of Italy's infrastructure and a lack of maintenance, adding that "those responsible will have to pay."

Italy's anti-establishment government which took office in June has pledged to increase public investments and lobby the European Commission to have the extra spending excluded from EU deficit calculations.

"The tragic facts in Genoa remind us of the public investments that we so badly need," said Claudio Borghi, economics spokesman of the right-wing League party, which governs with the 5-Star Movement.

The office of Prime Minister Giuseppe Conte said he was heading to Genoa in the evening and would remain there on Wednesday. Defense minister Elisabetta Trenta said the army was ready to offer manpower and vehicles to help with the rescue operations.

Train services around Genoa have been halted.

Shares in Atlantia, the toll road operator which runs the motorway, were suspended after falling 6.3 percent after news of the collapse.

REUTERS