In Borno and Yobe states, residents told DW that militants of the so-called Islamic State in West Africa (ISWA) — led by Musab al-Barnawi — held sway over a territory spanning an estimated 100 miles (160 kilometers). Boko Haram rebranded itself as ISWA when it aligned with Islamic State in 2015, the year President Muhammadu Buhari pledged to defeat the group.

"Definitely Boko Haram is very much present in our area. They even mount roadblocks, conducting stop and search operations the way the military does. Luckily they don't kill people in this area," said Ahmad Muhammad, who lives in Damboa, Borno State.

Residents also told DW the militants were collecting taxes from citizens in return for what they said was "protection". The Nigerian military has refuted the claims, insisting that no territory was under ISWA control.

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Mohamed Ibn Chambas, the UN Special Representative of the Secretary-General for West Africa and the Sahel, said he was not surprised by the accounts of the residents because it was wrong to assume Boko Haram was totally defeated.

"Unfortunately, this kind of struggle is difficult to eliminate completely in the short-run. What is not in doubt is that good progress has been made against Boko Haram. Most of their territory has been taken away and they have been pushed to remote areas and are being pursued there," Chambas said.

Hundreds of thousands have been internally displaced, especially women and children in northeastern Nigeria

Boko Haram "technically defeated"?

In 2015, President Muhammadu Buhari pledged to defeat Boko Haram, and officials insist this has been achieved. At the time he also told media that Nigeria had "technically won the war" against the militants. But the conflict, now in its tenth year, continues.

Despite offensive attacks launched by the multinational task force fighting Boko Haram

, the Islamists still pose a threat to countries in the Lake Chad basin.

In March this year, 20 Boko Haram militants were killed in clashes with Chadian soldiers who are part of the force. And because of these recent gains, the commander of the force, Major General Lucky Irabor, dismissed reports of militants controlling areas of Nigeria.

"Narratives can always be created by anybody for whatever purpose but you also need to verify. We have troops in Gaidam, in Gashua and even in Babban Gida. So, where do they control?" Irabor said.

Political analyst Umar Baba Kumo said the army may need a new approach in the face of a continued Boko Haram presence in the northeastern states.

"This is a very devastating development and a serious threat. People are becoming very apprehensive and disturbed that, despite the gains recorded, the militants are trying to revert to the situation we had faced. I think there is a need for the military to become more strategic and focused," Kumo told DW.

More than 20,000 people have been killed and hundreds of thousands displaced in the ten years of insurgency by Boko Haram in Nigeria, Chad, Cameroon, and Niger.

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