By Lanre Ola
MAIDUGURI, Nigeria (Reuters) - A suicide bomber killed six people inside a mosque in northeastern Nigeria's Borno state at dawn on Friday, an army spokesman said.
There was no immediate claim of responsibility for the attack in the town of Damboa but it bore the hallmarks of Islamist Boko Haram militants, who have waged an insurgency since 2009 to carve out a state based on sharia (Islamic law) in the northeast of Africa's most populous country.
Army spokesman Sani Usman said there were two suicide bombers involved, one of whom failed to gain entry to the Damboa Central Mosque and detonated his load in the street outside, killing himself but causing no other casualties.
He said the second militant managed to get into a smaller mosque nearby and blew himself up there, killing six worshippers and wounding one other person.
Earlier, a military source who did not want to be named said nine people were killed and 13 others injured in the 5:15 a.m. (0015 EDT) attack.
Damboa, 87 km (54 miles) south of the Borno capital Maiduguri, was the first town captured by Boko Haram, in July 2014. Security forces ousted the militants two months later.
Nigeria's army, aided by troops from adjacent countries, has retaken over the past year most of the territory lost to Boko Haram. But the jihadist group, which last year pledged loyalty to Islamic State, still regularly stages suicide bombings.
The insurgency has killed more than 15,000 people and displaced two million others.
(Writing by Alexis Akwagyiram; Editing by Mark Heinrich)