The armed group Boko Haram is better equipped than the Nigerian military fighting it, the governor of the region worst hit by the attacks said after more than 100 people died in a village raid.
"Boko Haram are better armed and are better motivated than our own troops," said Kashim Shettima after a meeting on Monday with President Goodluck Jonathan.
"Given the present state of affairs, it is absolutely impossible for us to defeat Boko Haram," Shettima was quoted by Reuters news agency as saying.
Jonathan ordered extra troops into northeast Nigeria in May to crush Boko Haram, which wants to create an Islamic state in the largely Muslim north.
The death toll from Sunday's raid on the village of Izge, near the border with Cameroon, was 106, Shettima said, up from an earlier estimate of 90.
Boko Haram sprayed homes with bullets, set off explosions and burned down dozens of houses in the attack.
Boko Haram remained able to "overrun communities and butcher innocent souls" despite the army presence, Shettima said.
Fatigued and over-stretched
Brigadier-General Chris Olukolade, an army spokesman, denied Shettima's statement.
"That cannot be true," he said. "Yes, they carry illegal arms, but are not better armed than the Nigerian army."
However, he acknowledged the "need for improvement" in the force.
Security analysts said Nigeria's military is fatigued and over-stretched in the vast and sparsely populated area of rocky hills where members of the armed group are hiding out.
Jonathan faces an election in a year's time, and the persistence of Boko Haram's more than four-year rebellion despite a costly counter-insurgency, remains a serious problem.
Nigerian forces, backed by air power, initially registered some successes, but Boko Haram retreated into the remote, hilly Gwoza area bordering Cameroon, from where they have mounted deadly attacks against civilians they accuse of being pro-government.
Last week, Boko Haram fighters in trucks painted in military colours killed 51 people.
Niger said on Monday it had arrested 20 militants plotting to attack a town in its territory, illustrating how Boko Haram also threatens Nigeria's neighbours, divided by porous borders on the cusp of the Sahara.