Dozens of corpses in military uniform have been brought to a Nigerian morgue after Boko Haram fighters last week launched an attack targeting security forces in the Yobe state capital of Damaturu, AFP reported Monday, citing a hospital source.
"We have received lots of bodies in the last three days from the attacks. I counted 35 bodies in military uniform," a senior official at the Damaturu Specialist Hospital told AFP.
It was not immediately clear whether the bodies belonged to troops or insurgents since members of the Islamist group have repeatedly used military uniforms as a disguise when they attack.
Boko Haram fighters armed with guns and explosives stormed Damaturu after dark on Thursday, torching four buildings and sparking a fierce gun battle.
Yobe state military spokesman Lazarus Eli said no data was available on a death toll, but did not deny reports alleging dozens of troops died in the attack.
Troop fatalities in Islamist clashes are rarely disclosed and officials are under pressure not to reveal such information.
Nigeria's sweeping offensive against Boko Haram has entered its fifth month and the military has described the Islamist group as being in disarray and no longer capable of attacking major population centres.
But the success of the operation remains unclear and the attack in Damaturu, apparently carried out by a significant number of insurgents in a heavily fortified city, has cast further doubt on the effectiveness of the military offensive.
President Goodluck Jonathan had declared a state of emergency across the northeast in mid-May and vowed to permanently end the uprising. Jonathan must now decide whether to extend the emergency measures when the six-month mandate expires next month.

The conflict has killed thousands since 2009.
Boko Haram has attacked Christians, Muslims, students, politicians and a range of other groups seen as opposed to the creation of a state governed by strict Islamic law.