20120609
AP
MAIDUGURI, Nigeria (AP) — Police say a suicide bomber has attacked their headquarters in the northeast Nigerian city of Maiduguri, killing three.

Borno State police chief Bala Hassan said the attack occurred Friday around noon.

He said one policeman and two civilians were killed and six civilians were injured.

Hours earlier, a suspected bomber died when an explosive went off prematurely in another part of the city.

No group immediately claimed responsibility. A radical Islamist sect known as Boko Haram has carried out similar attacks.

The U.S. Embassy issued a warning late Thursday to its citizens not to travel to Maiduguri as diplomats believe "the situation will continue to deteriorate."