At least 18 people have been killed in an explosion at a market in Maiduguri, north-eastern Nigeria, a medical worker has told the BBC.
The explosives were reportedly hidden in a vehicle carrying charcoal.
No group has said it carried out the attack but Maiduguri is the epicentre of the violent campaign waged by militant group Boko Haram.
Earlier, the Nigerian army said it had broken up a Boko Haram cell linked to the abduction of 200 schoolgirls.
“A van loaded with charcoal and IED [improvised explosive device] exploded at Monday Market in Maiduguri this morning. The location has been cordoned,” the defence headquarters said on its Twitter account.
The vehicle exploded into a huge fireball, AFP news agency quotes a witness as saying.
The BBC’s Habiba Adamu in the capital, Abuja, says a medical worker has reported that in addition to the 18 killed, 55 people were wounded in the blast.
“I heard a very loud explosion right from my house and rushed to the place,” one resident, Babagana Hausari, told the BBC.
“When I got there I saw many people lying after they were hit by explosives,” he said.
A suspected suicide bomber carried out the blast, Reuters news agency reports.
Cars and taxis, which were unloading passengers and goods, were wrecked, it says.
“I saw police and troops picking out victims,” said Alakija Olatunde, a student who rushed to the scene.