A parcel bomb with a timer exploded early this morning in front of a Florence bookstore run by a neo-fascist group, seriously wounding a policeman trying defuse the device, authorities said.

Anti-terrorism police discovered the package while patrolling sensitive sites and called in the bomb squad, Florence police chief Alberto Intini told RAI state television.

The package detonated as a police expert was approaching it at about 5.30am (04.30GMT), Intini said.

The officer was rushed to hospital where his left hand was amputated, a police source told Reuters. The blast also left him blind in one eye, the source said. Police are investigating and would not speculate on who placed the bomb or why.

"It's the third attack in a year on the bookstore," Gianluca Iannone, president of far-right group CasaPound, said in a statement. "It was a clearly political attack," he added.

In the 1970s and '80s, Italy was marred by far-left and far-right extremist attacks. In recent, years such violence has become much less frequent.