MILAN — Italy’s government has increased security at its diplomatic missions around the globe in response to “a crescendo of terroristic attacks” by an informal anarchist network acting in solidarity with an imprisoned Italian militant, the foreign minister said Tuesday.

Foreign Minister Antonio Tajani cited nearly a dozen attacks since the end of November, ranging from vandalism to explosive devices that have caused damage to Italian diplomatic targets in Argentina, Bolivia, Germany, Greece, Portugal, Spain and Switzerland. No injuries have been reported.

“It is obvious that there is an international solidarity (among anarchists) and therefore an attack against Italy, against Italian institutions, is being carried out across the world,” Tajani said, adding that security was being raised at all Italian embassies and consulates as well as the foreign ministry.

Tajani said they believe the network includes both Italians and anarchists from other countries acting in concert. He referred to graffiti scrawled in Catalan on the building housing the Italian Consulate in Barcelona.

The most serious of the attacks was the firebombing of two cars at the residence of an Italian diplomat in Athens in early December — one car was torched, and Tajani said only the failure of the second bomb targeting a car inside the garage of the residence and near a gas line averted worse consequences.

The attacks and as well as a series of protests, including one planned Tuesday in Madrid, are in solidarity with Alfredo Cospito, who has been on a hunger strike since October to protest a strict prison regime reserved for terrorists and mafiosi. The 55-year-old militant is serving a 10-year sentence for shooting in the leg an energy executive for a state-controlled company and 20 years for a series of dynamite attacks in Italy.

An appeals court in Turin last spring toughened his prison conditions to include solitary confinement except for one hour a day and a strict limit of family visits. The regime is imposed on prisoners who are considered to pose a danger even from inside prison.

Interior Minister Matteo Piantedosi said that the fact of the attacks only reinforces the necessity of the regime in Cospito’s case.

Cospito’s lawyers are currently appealing the strict conditions.

In the meantime, Cospito has been transferred from Sardinia to a prison south of Milan, which Justice Minister Carlo Nordio said was best equipped to deal with the health challenges of the hunger strike.

In Italy, anarchists on Monday torched cars belonging to the TIM telecommunications company, scrawling slogans denouncing Cospito’s treatment nearby. This weekend, a small group of his supporters clashed with police in Rome and two incendiary devices were lobbed in the parking lot of a police station in the capital. No one was injured.