A bomb blast at a public health college in Nigeria's second city of Kano killed at least eight people on Monday, in the latest violence to hit an area repeatedly attacked by Boko Haram.
File photo shows a police station in Kano's Sheka neighbourhood on January 25, 2012
Body parts, burnt-out vehicles and pools of blood were visible at the bomb site on the grounds of the School of Hygiene, which lies near the heart of the ancient northern city, an AFP reporter said.
It was not yet clear who carried out the attack but initial suspicion fell on Boko Haram, the Islamist extremists who have bombed many educational targets during a five-year uprising.
"So far 20 were taken to hospital and of that eight have been confirmed dead," Kano state police chief Aderele Shinaba told journalists at the scene.
A man believed to have planted the bomb, which went off at around 1 pm (1200 GMT), has been arrested and his car impounded, according to Shinaba.
The explosion came from a parking lot near the office of the school's provost, and while there were no classes on campus because of a term break, new students were reportedly on the grounds for registration.
Access to the area was being tightly restricted by the military who had deployed in large numbers around the college, causing massive traffic build-up in the congested city.
Attacks blamed on Boko Haram were once a near-daily occurrence in Kano, but the security services have had some success in containing the violence in recent months.
Much of the conflict has shifted to Nigeria's remote northeast, including the April 14 mass abduction by the insurgents of more than 200 schoolgirls from the town of Chibok, an attack which brought unprecedented global attention to the half-decade conflict.
Kano was hit by a suicide car bomb attack on May 19 in a mostly Christian area of the city, killing four people, including a young girl.
The military, which has been waging an offensive against Boko Haram in the northeast for more than a year, had claimed that the insurgents were on the run and no longer capable of attacking major population centres.
But a string of major attacks in key cities including central Jos, twin blasts on the outskirts of the capital Abuja and the bloodshed in Kano have reinforced the serious threat the Islamists pose to Africa's most populous country and largest economy.
Kano was also put on edge earlier this month amid clashes that followed the controversial appointment of the area's new Muslim monarch.
Boko Haram's uprising, which the group says is aimed at creating a strict Islamic state in the north, has left thousands dead since 2009.