POTISKUM, Nigeria — A man forced his way onto a bus at a crowded bus station and detonated explosives that killed 12 people and injured 20 in northeast Nigeria, according to the bus driver and hospital records.
The attack in Potiskum comes two days after a girl who looked about 10 years old detonated explosives that killed herself and four others at a market in the same town.
There was no immediate claim of responsibility for Tuesday's blast but it bore the signs of similar attacks by Nigeria's home-grown Boko Haram Islamic extremist group.
Bus driver Adamu Isa said a security guard stopped a man who set off a metal detector as passengers were boarding his bus.
"He was told to stand to one side but instead forced himself onto the bus and blew himself up," said Isa, who considered himself lucky to be alive.
Hospital records said the blast killed 12 people and wounded 20 who are being treated.
On Monday, a woman walked into a primary school in Fune, another area of Yobe state, and tried to give pupils a parcel to deliver to the headmistress. When they refused, she ran off, leading security agents to surmise she may have been carrying a bomb, teacher Mohammad Isa of Damagum Central Primary School told the Associated Press.
All schools in the area have been closed because of the possible threat.
Boko Haram is a nickname meaning "Western education is forbidden" in the local Hausa language. The militant Islamic group has carried out numerous attacks in the northeastern Yobe state.
Attacks by girls and young women have raised fears that Boko Haram is using some of its hundreds of kidnap victims to carry out bombings. It is unclear if children are detonating explosives, if the blasts are remotely controlled, and if the children understand what is happening.
At least 10,000 people have been killed in Nigeria's Islamic uprising in the past year, according to the Council on Foreign Affairs, and some 1.6 million people have been driven from their homes in the campaign to enforce strict Islamic law across Nigeria, whose 160 million people are divided almost equally between Muslims and Christians.