Nigeria's army arrested almost 500 suspected members of Islamist extremist sect Boko Haram in south-eastern Abia State, the military announced Tuesday.

The 144th battalion of the Nigerian army stopped a convoy of 33 busses and detained 486 alleged insurgents on the Enugu-Port Harcourt expressway, between the towns of Aro Ngwa and Imo Gate, according to local newspaper Daily Post. The arrests were made on Sunday but only announced to local media two days later.

The busses were coming from northern provinces and had mostly men between the ages of 16 and 24 years on board as well as eight women, according to military commander Colonel Rasheed Omolori.

Two busses managed to speed off, said Omolori. An investigation was under way.

Boko Haram, which means "Western education is sinful," has killed more than 1,500 people in numerous violent attacks in northern Nigeria since January.

The group abducted more than 200 schoolgirls from their dormitory in Chibok, on April 14. More than seven weeks after the kidnappings, there is no trace of the girls' whereabouts.