MAIDUGURI, Nigeria (Reuters) - Boko Haram freed 13 hostages, Nigeria’s presidency said on Saturday, after authorities negotiated their release with the Islamist militants.

The kidnappings were part of a campaign of attacks last year by the jihadist group whose bid to create an Islamic state in the northeast has killed at least 20,000 people and forced some 2.7 million to flee their homes since 2009.

Three of the hostages were lecturers from the University of Maiduguri who were abducted while on an oil exploration trip in Magumeri, in the northeastern Borno state, in July 2017. The other 10 were women police officers kidnapped in a raid on a convoy the previous month.

“Their release followed a series of negotiations as directed by President (Muhammadu) Buhari and was facilitated by the International Committee of the Red Cross, ICRC,” a presidency spokesman said in an emailed statement.

The ICRC said it had acted as a neutral intermediary in the hostage release.

“The ICRC was not involved in any negotiations that led to the handover of the 13 people. The armed opposition handed the 13 people over to ICRC representatives who transported them to Nigerian authorities,” it said in a statement.

The ICRC also acted as an intermediary in the release in October 2016 and May 2017 of some of the more than 200 girls kidnapped by Boko Haram from the northeastern town of Chibok in 2014.