A yet to be identified Nigerian UN peacekeeper has been killed and another injured by unidentified assailants in Timbuktu, in northern Mali.

A separate incident in Tessalit left three Chadian peacekeepers injured, BBC reports.

António Guterres the UN Secretary General has condemned the attacks, saying he is “deeply saddened” over the death of the peacekeeper.

He has called on the Malian authorities to bring the perpetrators to justice, and said that targeting UN peacekeepers “may constitute war crimes”.

Nearly 200 members of the UN mission have died since it was set up in 2013, making it the deadliest peacekeeping operation in the world.

Peacekeepers were deployed to Mali after Islamist militants seized the north of the country in 2012.