Attackers killed nine Nigerian construction workers early Monday in the restive northeastern city of Maiduguri, the base of the Islamist Boko Haram sect, the army said.
The victims, working at Shehu of Borno's Central Mosque in the city, were "massacred" by unknown assailants at around 1:45 am, said a statement from the Joint Task Force (JTF).
In a text message to AFP, a senior army officer, who asked not to be named, said they had been "slaughtered" by suspected members Islamist Boko Haram sect.
"Probably Boko Haram terrorists slaughtered them…They [the victims] are Nigerians," he said, without giving further details.
"The victims were living in a compound located at Bolori general area, Maiduguri Metropolis," said the JTF statement.
"JTF troops rushed to the area/compound and saw the dead bodies and they were deposited at the mortuary Borno State Specialist Hospital," it added.
No arrests had yet been made, he said.
Maiduguri, capital of Borno state, and Damaturu, capital of neighboring Yobe state, have repeatedly been hit by the radical Islamist group Boko Haram.
It is responsible for more than 1,000 deaths since the middle of 2009 in Africa's most populous nation and largest oil producer.
Gunfire and explosions rocked restive city of Damaturu on Saturday as security forces launched a pre-emptive offensive against Boko Haram Islamists, killing three suspected members.
The offensive followed intelligence that the extremist group were planning another attack on the city again, the deputy police spokesman of the state said.
On 19 June, the Nigerian authorities imposed a round-the-clock curfew on Damaturu for two days, following coordinated gun attacks on targets around the city that they attributed to Islamist militants.
It was partially relaxed after soldiers and police reclaimed control of the streets in an offensive that left at least 40 people dead, including 34 alleged Boko Haram members.
The Islamist group's insurgency, concentrated in Nigeria's mainly Muslim north, has frequently targeted the security forces, though the Islamists have also attacked Christian churches and other symbols of authority.
The government's response to Boko Haram in past months has included heavy-handed military raids.
But they have failed to stop the extremists and antagonized residents in the districts subjected to the raids.
Boko Haram initially said it was fighting for the creation of an Islamic state, but its demands have since shifted repeatedly. It is believed to have a number of factions, including a main Islamist wing.
Kano, Nigeria's largest city in the north, was the site of Boko Haram's deadliest attack yet, when coordinated bombings and shootings killed at least 185 people dead in January.
