Abuja, Nigeria - Nigerian authorities found improvised bombs in two primary schools in the northern city of Kano on Thursday, hours after the schools were attacked using explosives and gunfire by suspected militants from Islamist sect Boko Haram.
Boko Haram is waging an insurgency against Nigeria's government to try to impose stricter sharia (Islamic law) across Nigeria. It mostly targets authority figures and security forces, but has also struck civilians such as Christian worshippers.
It has become the top security threat in Africa's leading energy producer.
Blasts and gunfire were heard overnight in the Farawa and Sharada schools of downtown Kano, an ancient Islamist city that was a stopover on the trans-Sahara trade routes.
On Thursday, police found two unexploded bombs in one school and one in another.
"Our anti-bomb squad has combed the area and defused the unused explosives today," Kano police spokesman Magaji Musa Majiya said by telephone. "This was after the attacks carried out on the schools last night."
The first known attacks by suspected sect members against schools were in March, when it burned down 10 schools in its heartland in northeastern Nigeria's Borno state.
Boko Haram, which means "western education is sinful" is opposed to western influences in northern Nigeria, including in its schooling.
It rarely claims attacks, except the most high profile ones.
A spate of attacks last month, such as the killing of at least 15 people in a university theatre used for Christian worship, ended a relative lull and dampened hopes that recent killings and arrests of its members had weakened it.
Two policemen and a civilian were killed in an attack on the Mafa police station in Borno state on Saturday, the military said, saying they suspected the sect.