Gunmen assaulted police headquarters in Abuja, Nigeria's capital, and authorities fought off the assailants, according to the BBC.
“I can confirm that there was an attempted attack on the [Special Anti-Robbery Squad] this morning which was repelled,” spokesman Frank Mba said, the AFP reported.
No deaths were reported, though the BBC said unconfirmed reports suggested some prisoners housed in the building may have escaped.
As yet, no group has yet claimed responsibility for the attack, though many suspect the militant Islamist sect Boko Haram (its name roughly means "western education is a sin").
The group intends to enact strict Islamic law in Nigeria, which has a large Catholic population.
On Sunday, in Nigeria's Kaduna state, two car suicide bombers killed 11 people in a military church. No group claimed responsibility for the attack, but again, many suspect Boko Haram.
Today's attack comes as the Office of the Prosecutor (OTP) of the International Criminal Court (ICC) accused Boko Haram of crimes against humanity.
On November 22, the ICC said:
"The office has determined that there is a reasonable basis to believe that crimes against humanity have been committed in Nigeria, namely acts of murder and persecution attributed to Boko Haram.
"Therefore, the prosecutor has decided that the preliminary examination of the situation in Nigeria should advance to phase 3 (admissibility) with a view to assessing whether the national authorities are conducting genuine proceedings in relation to those who appear to bear the greatest responsibility for such crimes, and the gravity of such crimes," the report said.