Over 2,000 prisoners have escaped from Nigerian jails over the last five years following the intensification of attacks on the facilities by Islamist militant group Boko Haram. According to data released by the Nigerian Prisons Service until June 30, the country's 239 jails accommodate about 57,000 prisoners, only 32 percent of whom have been convicted.

Most of the 2,251 escaped prisoners are reportedly still at large, and several prison workers have been killed in the raids conducted by Boko Haram, BBC reported. Boko Haram recently also attacked a French cement plant in the northern part of the country and stole a large supply of dynamite, leading officials to suspect another round of jail breaks. In 2009 alone, 500 prisoners escaped from prisons in the northeastern city of Maiduguri, which is the group's stronghold, the BBC reported.

Soldiers who are tasked with defending towns and villages are also fleeing their posts, according to BBC, while officials struggle to contain the group's advance and prevent it from taking control of more regions in the country. On Monday, gunmen used explosives to break into a prison in the central state of Kogi, freeing 144 inmates and killing one person, Reuters reported. While 26 prisoners were recaptured by the police, the rest are still at large. Officials did not confirm whether any of the inmates belonged to Boko Haram.

Boko Haram, whose name means “Western education is sinful,” is trying to establish an Islamic caliphate in Nigeria, and has conducted several kidnappings and attacks to challenge the government's authority in the Muslim north. In July, the group had kidnapped more than 200 schoolgirls and later claimed that they had been converted to Islam and had been married off. The group has more than 500 women and young girls in its custody, according to a report.