Gunmen ambushed Kuje prison near Nigeria's capital city of Abuja, freeing around 600 of the nearly 900 inmates late Tuesday. Bandits attacked the maximum-security prison with guns and high-grade explosives. One security officer was killed during the raid and three others were injured.

Half of the escaped prisoners are now back in police custody, according to officials.

"They have reported themselves to the police, some we have successfully retrieved from the bushes where they were hiding, and (as of) now we have retrieved about 300 out of about 600 that got out of the jail cells," said Shuaib Belgore, who serves as the permanent secretary at Nigeria's Interior Ministry. 

Belgore pointed to Boko Haram as collaborators in the attack and said that the gunmen came "specifically for their co-conspirators."

"Some of them are in the general (prison) population so they broke out and other people in that population escaped as well but many of them have returned," Belgore said. Kuje prison housed 64 suspected members of the Boko Haram extremist group — all of whom are still on the run.

While the Kuje prison raid was the first to occur in the capital, rebels have conducted several similar jailbreaks in northeastern Nigeria.

Rebels attack presidential convoy

The attack occurred around the same time as an ambush carried out by rebels on a presidential convoy. The motorcade was en route to the hometown of President Muhammadu Buhari in northern Nigeria. Buhari was not present at the time. 

"Attackers opened fire on the convoy from ambush positions but were repelled by the military, police and security personnel accompanying the convoy," a presidential spokesman said in a statement.

The two incidents underscore growing security concerns in Nigeria. Extremist violence is a primary security challenge for Africa's most populous country. Violence carried out by Boko Haram and an off-shoot group calling itself "Islamic State Central African Province" has caused more than 35,000 deaths and displaced over 2 million people in Nigeria, according to the UN.

asw/dj (Reuters, AFP, AP)