MAIDUGURI, Nigeria 

The Islamic State in West Africa Province (ISWAP) terrorist group claimed responsibility late Wednesday for an attack on a maximum-security prison in Nigeria’s capital.

In a 38-second video released by the Islamic State's Amaq news agency, the group said its fighters carried out the assault on Kuje Prison in Abuja.

“Fighters of Islamic State attacked Kuje prison in Abuja yesterday and succeeded in freeing dozens of prisoners," the group said in the video.

Members of ISWAP were seen in the video walking towards the prison, firing sporadically and shouting as some vehicles outside the facility were on fire.

They invaded the prison with explosives late Tuesday, shooting sporadically.

The spokesman for the Nigerian Correctional Service, Abubakar Umar, issued a statement after the attack.

“Four inmates are dead and 16 inmates sustained various degrees of injuries and are being treated at the moment," he said.

He said 879 inmates escaped from the facility during the attack and 443 have been recaptured while the rest are still at large.

He also confirmed the presence of some high-profile convicts in the prison, including a former anti-crime police officer serving a jail term for a drug-related case.

Nigerian President Muhammadu Buhari, speaking to journalists during a visit to the prison to assess the aftermath of the attack, said he was disappointed over the failure of the intelligence system.

“Saddened by the attack on the Medium Security Custodial Centre, Kuje. I am disappointed with the intelligence system. How can terrorists organize, have weapons, attack a security installation and get away with it? I am expecting a comprehensive report on this shocking incident,” he said later on Twitter.

Buhari said regular intelligence sharing was needed to halt such incidents. ​​​​​​​

More than 60 Boko Haram terrorists arrested by security agencies were being held in Kuje Prison, a top military source told Anadolu Agency.