Around 440 inmates are on the run after a suspected raid by Islamist Boko Haram militants on a prison in Nigeria's capital Abuja on Tuesday night, an interior ministry official said.
The raid, and a separate ambush on an advance convoy of Nigerian President Muhammadu Buhari - who was not present - heading to his hometown in the northern state of Katsina, highlights Nigeria's going security challenges, especially in northern regions where armed insurgents and gangs are rife.
Shuaib Belgore, permanent secretary at the interior ministry, told journalists outside the Abuja prison - which has 900 inmates - that a security officer was killed during the raid and three others were injured.
He said the suspected Boko Haram attackers came for members who were held in the prison.
"They came specifically for their co-conspirators, but in order to get them ..., 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.
A total of 879 inmates fled, the prison service said in a statement, with 443 still at large and the rest recaptured. It said four inmates were dead and 16 others injured.
"They have reported themselves to the police, some we have successfully retrieved from the bushes where they were hiding," Belgore said.
Outside the prison, the charred remains of several vehicles with bullet holes were seen on Wednesday morning, attesting to gunbattles in the vicinity during the raid.
A helicopter hovered overhead as armed security officials brought in a shirtless inmate limping with a gaping wound on his leg, while another injured inmate was carried into the prison.
Buhari was not in the convoy of cars carrying an advance team of security guards, protocol and media officers heading to the president's hometown Daura, near the border with Niger, to prepare for the Muslim Eid al-Adha holiday.
"The 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.