Bomb blast rocks Venice

Italian police patrol the wreckage of the exploded Venice courthouse

VENICE, Italy -- An explosion inside a courthouse has rocked Italy's canal city just hours before Prime Minister Silvio Berlusconi was due to visit.

No one was seriously injured in the blast which detonated at about 3:30 a.m. (0130 GMT) on Thursday in the boiler room of the courthouse near the city's Grand Canal.

Two policemen on routine patrol outside the courthouse escaped the explosion with minor injuries.

The building was severely damaged and windows of shops as far as 200 yards away shattered in the blast.

Berlusconi appealed for calm and said he would go ahead with the trip as planned, accompanied by the minister for infrastructure and transport Pietro Lunardi who hoped to finalise projects for construction in the area.

The prime minister also revealed he had received threatening letters and bullets through the post, as had interior minister Claudio Scajola and several other members of the centre-left opposition party.

"There is a worrying escalation of violence," Berlusconi told journalists at his office after learning of the Venice bomb.

The prime minister said Italian institutions had become the target of "an international movement that was not born in Italy but appears to have as its aim a fight against the Italian government," reported The Associated Press.

Police initially suspected the explosion was the result of a gas leak after witnesses said a strong smell of gas lingered near the courthouse building shortly after the blast.

While there was no confirmed link between the bomb blast in Venice and Berlusconi's visit, the city's mayor Paolo Costa told AP: "My feeling is that this is an attack that wants to send a signal to someone."

After the blast, police began checking the underground sewer network and lifting manholes to check for more hidden devices.

The Venice police chief was cutting short his holiday and returning to the city, said AP.