DAMATURU, Nigeria (Reuters) - Unidentified suicide bombers killed 17 people in three blasts in the northeastern Nigerian city of Damaturu on Wednesday, a spokesman for the governor of Yobe state said.
Nobody claimed responsibility for the attacks, but Nigeria has stepped up efforts to end the six-year insurgency of militant Islamist group Boko Haram, during which it has killed thousands in shootings and bombings.
Last week, Boko Haram, which has pledged allegiance to hardline militants Islamic State, claimed two suicide bombings in the capital Abuja that killed at least 15 people.
Wednesday's coordinated attacks, the worst to hit the capital of Yobe since July, were carried out shortly after 6am (1:00 a.m. EDT) near a mosque and shops in the suburbs.
The State Emergency Management Agency (SEMA) in Yobe said the three suicide bombers were teenage boys.
"Seventeen people lost their lives and 11 others injured," said Abdullahi Bego, a spokesman for Yobe state governor Ibrahim Gaidam.
Boko Haram has killed 900 people since May when President Muhammadu Buhari took office, promising to crush the insurgency. The group controlled territory as big as Belgium at the end of 2014, but has since been dispersed by Nigerian troops with help from neighboring Chad, Niger and Cameroon.
"We denounce lies by the authorities that our brethrens numbering about 200 have surrendered to them, and that they have also rescued women and children. All these are lies," one Boko Haram member said in the 17-minute video posted on YouTube.
In late September, the military said at least 200 Boko Haram fighters had surrendered to Nigerian troops at Banki, a commercial town near the border with Cameroon.
Boko Haram's leader Abubakar Shekau, whose failure to appear on screen in any of the group's messages since February has prompted speculation about whether he is alive, was referred to in the latest film but was not shown.
(Reporting by Joe Hemba, additional reporting by Isaac Abrak; Writing by Alexis Akwagyiram; Editing by Raissa Kasolowsky)