KANO, Nigeria — Radical Islamic fighters killed seven foreign hostages in Nigeria, European diplomats said Sunday, making it the worst such kidnapping violence in decades for a country beset by extremist guerrilla attacks.
Nigeria’s police, military, domestic spy service, and presidency remained silent over the killings of the construction company workers, kidnapped Feb. 16 from northern Bauchi state.
The government’s silence only led to more questions about the nation’s continued inability to halt attacks that have killed hundreds through shootings, church bombings, and an assault on the United Nations.
The latest victims were four Lebanese and one citizen each from Britain, Greece, and Italy.
Britain and Italy said all seven of those taken from the Setraco construction company compound had died at the hands of Ansaru, a previously little-known splinter group of the Islamist sect Boko Haram. Greece also confirmed one of its citizens was killed, while Lebanese authorities did not immediately comment.
‘‘It’s an atrocious act of terrorism, against which the Italian government expresses its firmest condemnation, and which has no explanation, if not that of barbarous and blind violence,’’ said a statement from Italy’s foreign ministry.
Italy also flatly denied a claim by Ansaru that the hostages were killed before or during a military operation by Nigerian and British forces, saying there was ‘‘no military intervention aimed at freeing the hostages.’’
Italian Premier Mario Monti identified the slain Italian hostage as Silvano Trevisan and promised Rome would use ‘‘every effort’’ to stop the killers. British Foreign Secretary William Hague called the killings ‘‘an act of cold-blooded murder’’ and identified the UK victim as Brendan Vaughan.
Ansaru issued a statement Saturday saying its fighters kidnapped the foreigners from the construction company’s camp at Jama’are, a town about 125 miles north of Bauchi.
In the attack, gunmen first assaulted a local prison and burned police trucks, authorities said. Then the attackers stormed the construction company’s compound, killing a guard in the process, witnesses and police said.
In an online statement Saturday, Ansaru said it killed the hostages in part because local Nigerian journalists reported the arrival of British military aircraft to Bauchi. Ansaru said it believed the planes were part of a rescue mission for the abducted hostages.
However, Ansaru’s statement cited local news articles that instead asserted the airplanes were spotted at the international airport in Abuja, the nation’s central capital about 180 miles southwest.
The UK Defense Ministry said the planes it flew to Abuja ferried Nigerian troops and equipment to Bamako, Mali, where a coalition of forces are fighting radical Islamists.