Nigerian police have arrested eight members of the Islamist terrorist group Boko Haram over the 2014 abduction of more than 200 schoolgirls from the town of Chibok.

The men "confessed to having participated actively in the kidnapping of the Chibok schoolgirls," police commissioner Damian Chukwu told journalists in the northern town of Maiduguri, once a Boko Haram stronghold.

The eight men were among a group of 22 insurgents arrested within the past two weeks, according to Chukwu.

One of the men, aged 23, "confessed to being one of the Boko Haram commanders who coordinated and led the kidnapping" of the Chibok girls, Chukwu added.

The kidnapping of the Chibok girls captured the world's attention, with celebrities and prominent personalities such as former US first lady Michelle Obama joining a "Bring Back Our Girls" campaign to free them.

Boko Haram has kidnapped thousands of other women and children over the past few years, forcing them into sexual slavery or into marriages with its fighters.

The extremists, who have been active since 2009, want to enforce a strict interpretation of Islamic law, or sharia, in Nigeria, as well as in bordering regions of Cameroon, Chad and Niger.

Tens of thousands of people have died at the hands of Boko Haram in the region and an estimated 2.5 million people fled their homes.