A small package of explosives that blew up by the door of a Spanish-language school in Rome this morning damaged the building and cars but injured no one.
"There was no threat beforehand, no warning, nothing," said Mr Jose Maria Jimenez Serrano, the head of the Cervantes school, which has 170 pupils from nursery to high-school age.
Police said the package contained around half a kilogramme of high-explosive powder stuffed into a small metal cylinder.
Police said the motive was unclear but it may have been an act of vandalism.
Spanish media speculated that the blast may have been the work of the Basque separatist group ETA.
Basque terrorists set off bombs in a number of Italian cities in the 1990s, but there have been no recent attacks in Italy linked to the group.