Parcel bombs exploded at the Swiss and Chilean embassies in Rome on Thursday, wounding two people, days after a suspect package found on an empty train in Rome's metro system.
Bomb threats were also called in to Rome's City Hall and several other government offices, the mayor's office said, though no bombs had been found in either location.
Police were conducting checks at all embassies in the capital after Thursday's explosions, which wounded the two people who opened the packages, one seriously. Italian media said the victim at the Swiss Embassy was a 53-year-old Swiss national, who risks losing both his hands, although his life is not in danger.
The bombings come after violent anti-government protests rocked Rome over the past week, and ongoing security alerts across Europe this month.
On Wednesday, the police blanketed the capital in heavy security due to a student protest against education reform.
Reports about who might have sent the packages and why ranged from anarchists to "eco-terrorists."
While the suspect package found in Rome's metro system that triggered a bomb alert Tuesday contained cement and not gunpowder, as stated earlier by officials, the head of the Carabinieri police force in Rome, said that it was made by "an expert" and could have been a kind of warning. The Corriere della Sera daily said in an editorial that the suspect package "could have been aimed at criminalizing those who protest."
In November, police discovered 14 parcel bombs sent from Greece to various embassies in Athens. Other parcel bombs were addressed to European targets including the leaders of Germany and Italy.
Italian Foreign Minister Franco Frattini on Thursday released a statement of solidarity with "the Swiss ambassador and with all the staff of the Embassy. They were victim of a violent act that we firmly condemn."