Seven people have been killed and two are missing after a container ship crashed into a concrete control tower in the northern Italian port of Genoa.

The tower, which was 50 metres high, collapsed into the sea late last night after being struck by the vessel, the Jolly Nero.

Three coastguard officers are among the dead.

Divers are searching for two missing people at the site and cranes are sifting through debris along the shore.

The other victims have yet to be identified.

Two bodies were recovered today from the wreckage of the tower's lift, a fire department spokesman said.

The accident happened as workers were changing shifts and there were 13 people in the tower when it was struck, the coastguard said.

As well as the dead and missing, officials said four other people were injured and were taken to hospital.

Two were seriously hurt and a third has lost a foot, investigators said.

"The main injuries are fractures, crushed body parts, significant traumas," said emergency services doctor Andrea Furgani.

The crash occurred shortly after 11pm in calm conditions as the Jolly Nero was manoeuvring out of the port.

Genoa prosecutor Michele Di Lecce has opened an investigation and is focusing on a possible malfunction of the ship's engine.

The captain of the Jolly Nero and the harbour pilot on the ship's bridge are under investigation, but such investigations are normal in Italy.

In testimony to parliament after visiting the port, Transport Minister Maurizio Lupi also said an engine problem could be behind the incident, which took place in "perfect" weather conditions.

Other causes could have been a human error or problems with tow cables fixed to two tug boats that were accompanying the ship out of the harbour, Mr Lupi said.

The crash is the most serious maritime accident in Italy since the Costa Concordia liner struck a rock and capsized off the island of Giglio in January 2012, killing 32 people.

"There's no logical explanation because two tug boats were moving the ship and there was a port pilot on board and sea conditions were optimal," the head of the Genoa Port Authority, Luigi Merlo, said.

All that is left of the tower is a leaning metal stairway.

The Jolly Nero, which is 238 metres long with a gross tonnage of 40,594 tonnes, is owned by local operator Ignazio Messina and Co.

"A thing like this has never happened, we are devastated," said Stefano Messina, one of the directors of the family-owned firm, who was in tears when he spoke to a local TV channel.