UN Secretary-General Ban Ki-moon on Saturday welcomed an African Union proposal to set up a regional five-nation force of 7,500 troops to fight Nigeria’s Boko Haram extremist militants.

UN Secretary-General Ban Ki-moon on Saturday welcomed an African Union proposal to set up a regional five-nation force of 7,500 troops to fight Nigeria's Boko Haram extremist militants.

Support for the initiative, announced at an African Union summit being held in Ethiopia's capital Addis Ababa, came hours after the Chadian military said three soldiers and 123 militants were killed in two days of fighting with a Chadian army contingent in northern Cameroon.

"I welcome the decision of the AU and regional countries to establish an MJTF (Multinational Joint Task Force) against Boko Haram," Ban told reporters on the sidelines of the summit.

"They have committed unspeakable brutality. Those terrorists should be addressed with a regional and international cooperation. Not a single country, even the regional countries, can handle this alone," he said. "The United Nations is ready to fully cooperate with the African Union."

Ban nevertheless said that "military means may not be the only solution."
"There should be very careful analysis of the root causes why this kind of terrorism, and extremism, violent extremism, are spreading," he told reporters.

At least 13,000 people have been killed and more than a million forced from their homes by Boko Haram violence since 2009. The group also carried out the mass abduction of 276 girls from the town of Chibok in April last year.