Despite military successes scored against Boko Haram militants, it will take years to "completely eliminate" the group, a United Nations envoy has told Agence France Presse.
"Boko Haram has proven to be a resilient group...I think it will take time to totally eliminate," said Muhammad Ibn Chambas, special envoy to the UN secretary general for West Africa and the Sahel.
"What we are seeing is that Boko Haram has become part of an international terrorism network."
Chambas was speaking on the sidelines of a Lake Chad regional summit in Maiduguri, the capital of Borno state and birthplace of Boko Haram.
Governors from four countries straddling the lake ---- Nigeria, Niger, Chad, Cameroon --- have met for two days to discuss regional cooperation on stabilization, peace building and sustainable development in the area, AFP reported.
Chambas said that the insurgents were likely still holding on to territory in the region.
"It is relative," he said in response to reports that Boko Haram was holding territory in the northeast states of Yobe and Borno.
"As long as they are not totally defeated obviously they are present in some areas".
The four countries formed the Multinational Joint Task Force (MNJTF) to fight the extremists who criss-cross the porous borders in the remote region.
"We of course ask that the MNJTF remains vigilant in its fight against Boko Haram, we cannot take it for granted and assume they have been totally defeated," said Chambas.
The insurgency has killed at least 20,000 people in nine years of violence that has spilled from northeast Nigeria into Niger, Chad and Cameroon, creating a dire humanitarian crisis.
