Nigeria's President Muhammadu Buhari says the army has seized one of Boko Haram's last bases in northeastern Borno state.
If confirmed, the claim would mark a key stage in the government's months-long offensive against the armed group.
A long campaign in the 1,300sq km forest in Borno led to the "final crushing of Boko Haram terrorists in their last enclave in Sambisa Forest" on Friday, Buhari said in a statement on Saturday.
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He congratulated his troops for "finally entering and crushing the remnants of the Boko Haram insurgents at 'Camp Zero', which is located deep within the heart of Sambisa Forest".
"The terrorists are on the run, and no longer have a place to hide. I urge you to maintain the tempo by pursuing them and bringing them to justice," he said.
But Al Jazeera's Ahmed Idris, reporting from Abuja, said that it was not the first time the government claimed that Boko Haram was "dealt with a death blow".
"In 2015, Buhari and the Nigerian army said that Boko Haram was technically defeated and that they did not have the capacity to launch an attack or hold territory in northeast Nigeria.
"But at the end of the rainy season, we saw an emboldened Boko Haram trying to attack military convoys, isolated villages and launching more suicide attacks, especially in Borno state."
The seven-year-old conflict with Boko Haram has killed more than 15,000 people and displaced more than two million in the northeast of Africa's most populous nation.
Boko Haram controlled a very large expanse of Nigeria's northeast in early 2015, but the fighters were pushed out of most of that territory over the last year by Nigeria's army and troops from neighbouring countries.
They moved to a base in the Sambisa Forest, a former colonial game reserve.
The military has said in the last few days that the fighters are running away from the forest into surrounding areas and people have been told to be vigilant.
Al Jazeera's Idris added that authorities have called on civilians to cooperate with security forces amid fears that Boko Haram members had infiltrated communities in the proximity of the forest.
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Source: Al Jazeera and news agencies