At least five railway workers were killed, two other injured after being hit by a train while conducting overnight maintenance works in northern Italy, officials and firefighters said Thursday.

The train, which was transporting wagons on the Milan-Turin line and had no passengers, was travelling at 160 kph (99 mph) when it hit the team replacing parts of the track near Brandizzo, on the outskirts of Turin, Italian news agencies said.

"Five workers were killed by a passing train, two others injured," the fire service said in a brief statement.

The bodies of the men, reported to be aged between 22 and 52 years old, were said to have been dragged for several meters.

Two of their colleagues were unharmed but remain under observation in hospital, while the train driver was in shock but uninjured, according to Italian news agencies.

RFI, the company which manages Italy's rail network, confirmed that five workers from an external contractor died when a train "not in commercial service" hit them shortly before midnight.

It offered its "deep sorrow" and condolences for the families of the victims, and said investigations were underway.

Paolo Bodoni, the mayor of Brandizzo, told the AGI news agency an emergency worker had described to him a "chilling scene, with human remains across 300 metres."

"It's a huge tragedy," he said.

"It cannot be excluded that there could have been a communication error," he said, but said that would be a matter for investigations.

The train line between Turin and Milan remained suspended early Thursday morning.

Turin Mayor Stefano Lo Russo described it as a "huge tragedy, which leaves us all shocked," offering his thoughts to the families of those killed.