Eight suspected members of Islamist militant group Boko Haram have confessed to involvement in the 2014 abduction of some 270 girls from the town of Chibok, the Nigeria Police Force said on Wednesday.

The mass abduction of girls from their school caused global outrage and drew attention to the militant group which has killed more than 30,000 people since 2009 in an insurgency aimed at creating an Islamic state in northeast Nigeria.

Abba Kyari, deputy commissioner of police, said 22 suspected members of the militant group were arrested in different locations in the neighbouring northeastern states of Yobe and Borno.

“Eight of them, including a commander, have confessed to be involved in the planning and kidnap of Chibok girls,” Kyari said.

“It was an intelligence-led operation. We have been monitoring them for about six months to one year,” said Kyari, who led the team.

Many of the girls managed to escape in hours following their abduction or were released in the last few years, including 82 who were released in an exchange deal that included several imprisoned senior members of Boko Haram, but around 100 are still being held.

Boko Haram was pushed out of most of the territory it held in three northeastern states in early 2015 by Nigerian troops, backed by soldiers from neighbouring countries, but the group continues to carry out kidnappings, gun raids and bomb attacks.

- Reuters