A female suicide bomber has blown herself up in a college campus in northern Nigeria's biggest city of Kano, killing three people and critically wounding another seven, on the same day authorities arrested a 10-year-old girl with explosives strapped to her chest.
The bomber targeted youths who were looking at a notice board for national youth service in Kano State Polytechnic.
Wednesday's attack was the fourth such attack by a woman in Kano in less than a week, a security source said.
Government spokesman Mike Omeri also confirmed the attack in a statement to the AFP news agency.
"At about 2:30pm [13:30 GMT], another female suicide bomber exploded an improvised explosive device at the Kano State Polytechnic."
In a separate incident in the northern Katsina state, security forces arrested three suspects believed to be members of the armed group Boko Haram, including an underage girl with explosives on her body, the government spokesman said.
The "10-year-old ... was discovered to have been strapped with an explosive belt," Omeri said.
The two other suspects were a man and an 18-year-old girl who attempted to flee from authorities at a checkpoint, the government spokesman told Al Jazeera's Rawyah Rageh in Nigeria.
The news came as authorities also reported on Wednesday that 13 people were killed and 35 injured when two mosques in northern Yobe state were bombed on Tuesday night at the close of Eid al-Fitr, the Muslim holiday marking the end of Ramadan.
Boko Haram, which is fighting for an Islamic state in religiously mixed Nigeria, has repeatedly attacked several locations in northern Nigeria in recent months.
Two female suicide bombers blew themselves up at a trade show and a petrol station in Kano on Monday, killing one other person and injuring at least six others.
On Sunday, a female suicide bomber killed herself but no one else while trying to target police officers.
Though much of the violence is concentrated in the remote northeast, Boko Haram has struck in several bomb attacks across Nigeria since April.
On Sunday, the group staged a cross-border attack into Cameroon, killing at least three people there and kidnapping the wife of the vice prime minister.