Police say suicide bombers attacked a checkpoint in Nigeria's northeastern city of Maiduguri, killing two of themselves. Two other explosions occurred hours later.

It was the fifth attack in three weeks on the city that is the birth place of Nigeria's homegrown Boko Haram Islamic extremist group.

Police spokesman Victor Isuku says police challenged two women and a man running toward their checkpoint opposite the Federal High Court before dawn Friday. One woman detonated, killing herself and the male accomplice. The other woman has been arrested.

No details were immediately available about two blasts that rang out around 8 a.m. (0700 GMT).

Boko Haram has recently stepped up attacks after a months-long lull in the Islamic uprising that has killed more than 20,000 people over seven years.