Maiduguri: A truck exploded in a huge fireball killing at least 15 people today in the northeast Nigerian city of Maiduguri, the latest attack in a city repeatedly hit by Boko Haram Islamists.

The bomb rocked Maiduguri's largest roundabout near the crowded Monday Market where elderly women line the road selling peanuts and kola nuts as snacks to morning commuters. The defence ministry said in a tweet that an "improvised explosive device" went off in "a van loaded with charcoal" and that the area had been cordoned off.

Unruly crowds tried to attack firefighters deployed to the scene, accusing of them of arriving too slowly and hindering their efforts to put out the raging blaze, an AFP photographer said. An AFP reporter said elderly women and poor children who beg at the roundabout were among the casualties. Victims were taken to the State Specialist Hospital, where the photographer saw the bodies of 15 people killed in the blast, while witnesses said the toll could be much higher. While there was no immediate claim of responsibility, blame was likely to fall on Boko Haram, which was founded in Maiduguri more than a decade ago and has killed thousands during a five-year uprising.

Attacks in the city were once a daily occurence but a huge military offensive launched last year and backed by vigilante fighters had some success in flushing the insurgents out of the city into the remote corners of Borno state, of which Maiduguri is the capital. But those gains appear to have been lost following a series of attacks in the city this year targeting civilians and the security services.

A bomb ripped through a crowded market in January. In March, hundreds of Islamists stormed the military's Giwa Barracks in Maiduguri, a notorious army prison, and set free scores of their brothers in arms.

The insurgents' kidnap of more than 200 schoolgirls in April from the remote town of Chibok in Borno state provoked international outrage and drew unprecedented global attention to the Islamist uprising. Today's attack came less than 24 hours after Nigeria's military said it had broken up a Boko Haram intelligence cell and arrested its leader, alleged to have taken part in the abduction of the schoolgirls.