At least 19 people have been killed in Nigeria, the police say, following an hours-long gunfight punctuated by explosions in the country's northeast.
The violence on Tuesday evening, which authorities blamed on the armed Islamist group Boko Haram, targeted the cities of Kano and Maiduguri, where the group once had its main mosque.
The heaviest fighting occurred in Maiduguri, with soldiers firing on suspected group members for several hours as bomb blasts echoed across the city, witnesses said.
Colonel Victor Ebhaleme, a military spokesman, said on Tuesday that all those killed were "Boko Haram terrorists" and that the military suffered no casualties on its side.
Soldiers also recovered weapons and ammunition in the operation which targeted areas authorities believed served as hideouts for Boko Haram in the arid, dusty city, Ebhaleme said.
A man who lives in the neighbourhood where the fighting took place later said that some civilians had been struck stray bullets in the fighting.
"I almost got home, but I saw soldiers shooting and I had to run back on foot," the man said. He spoke on condition of anonymity as he feared angering either the military or Boko Haram.
The crowded neighborhood, called Lawan Bukar, is close to the palace of the region's traditional ruler, the Shehu of Borno.
It is also in an area where suspected Boko Haram members recently beheaded two civilians and shot dead a politician.
Meanwhile, in Kano, armed men suspected to belong to Boko Haram opened fire and killed a retired deputy inspector-general of Nigeria's federal police, as well as two other officers in the city.
Rilwan Mohammed, Kano state police spokesman, confirmed the attack took place, but declined to offer additional details.
Nigeria faces a growing wave of sectarian violence blamed on Boko Haram, whose name means "Western education is sacrilege" in the Hausa language of Nigeria's predominantly Muslim north.
Boko Haram has been accused of killing more than 560 people this year, according to an AP news agency count.
The group’s targets have included churches, often attacked by suicide car bombers.
It most recently claimed responsibility for a suicide car bombing that struck a church in the northern state of Bauchi on Sunday that killed at least 15 people and wounded dozens more.