Rome is on high alert Christmas Eve, one day after mail bomb explosions at the Chilean and Swiss embassies in the Italian capital seriously wounded two people.
The Italian news agency ANSA reports an anarchist group has claimed responsibility for Thursday's attacks in a note found at one of the blast sites.
ANSA reports the Informal Anarchist Federation says it has decided to make its voice heard with words and action.
Interior Minister Roberto Maroni has said the bombings are probably linked to what he calls "very violent" anarchist groups that also are present in Spain and Greece and are closely tied.
Italian Foreign Minister Franco Frattini condemned the bombings.
Thousands of tourists and pilgrims have been pouring into Rome this week for Christmas ceremonies at the Vatican.
Thursday's blasts in Rome are similar to a wave of parcel bombs in Greece last month that targeted Western leaders and embassies. One person was wounded in those attacks.
The attacks Thursday came amid increased concern in Europe about possible holiday season attacks, after a recent suicide bombing in Stockholm and this week's arrests of 12 terror suspects in Britain.
Some information for this report was provided by AP and AFP.