New Delhi/UNI: United Nations Secretary-General Antonio Guterres strongly condemned the attack against a police patrol of the UN mission in Mali on Friday, which killed two Nigerian peacekeepers and injured four others.

An unidentified gunman shot and killed two officers, including one woman from the United Nations Multidimensional Integrated Stabilization Mission in Mali (MINUSMA), while they were on patrol near the city of Timbuktu, according to mission head El-Ghassim Wane.

Through a statement, the UN chief extended his deepest condolences to the bereaved families, as well as to the government and people of the Federal Republic of Nigeria.

Guterres recalled that attacks targeting UN peacekeepers may constitute war crimes under international law.

He called on the Malian authorities to spare no effort in identifying and swiftly bringing the perpetrators of these heinous attacks to justice.

Mali has been grappling with an armed rebellion since 2012.

Thousands of people have been killed and hundreds of thousands have fled their homes.

MINUSMA was established on April 25, 2013 by the Security Council Resolution 2100 to stabilize the country after the Tuareg rebellion of 2012.

It has become the UN's most dangerous peacekeeping mission, with more than 200 peacekeepers killed out of a force of about 15,200 so far.