Nigeria's head of counter-terrorism on Friday accused neighbouring Cameroon of failing to make a serious effort to drive Boko Haram insurgents from its territory.

Sarkin-Yaki Bello, Coordinator-General Counter Terrorism Centre, said regional efforts against the Islamist insurgency had improved over the years but more needed to be done.

"Niger has been proactive and aggressive, Chad has shown zero tolerance for Boko Haram," he told Reuters in an interview.

"Cameroon, we've engaged them to be more pro-active. They haven't really. Not yet."

Bello's made his comments at a time of renewed international attention on Boko Haram following its kidnapping of more than 200 schoolgirls in northeast Nigeria last month.

The girls have still not been rescued despite a military operation involving foreign experts, and Nigeria's security forces have been bruised by criticism, both internal and international, for their slow response to the hostage crisis.

Bello declined to comment on where the girls were or efforts to free them. But he said he feared a rescue could be lethal given the Islamist tactic of killing hostages during a such attempts.

"We want to bring them out alive," he said.

He also ruled out any prisoner swap. "If you let them out, the terrorists get stronger. We also need to protect those they haven't yet killed or kidnapped."

West African leaders met in Paris two weeks ago to discuss the threat and pledged to co-operate in waging "total war" on the insurgents.

Though a homegrown Nigerian problem, the success of any effort to defeat Boko Haram will depend partly on the neighbours that share its sparse, semi-arid borderlands.

President Goodluck Jonathan declared a state of emergency in northeast Nigeria a year ago but Boko Haram retreated to the Cameroon border. It has launched near daily hit-and-run attacks for the past year from the Mandara mountains between Cameroon and Nigeria.

Bello said there had been decades of poor communication between the two countries that hampered cooperation. They have had a border dispute since gaining independence in the 1960s from the British and French colonialists that carved them up.

Cameroon's information minister, Issa Tchiroma Bakary, denied his country was dragging its feet, pointing to its sending of troops in its Far North region to counter the Boko Haram threat.

"Cameroon has never been the weakest link in the chain," Tchiroma told Reuters by telephone from Yaounde. "As the deployment of troops and equipment in the past few days prove, we have put up an iron curtain with enough firepower, which Boko Haram cannot break."

Jonathan said on Thursday he had ordered an offensive against Boko Haram, but efforts to crush them have thus far been ineffective and it has shown remarkable resilience in five years of fighting the Nigerian government to set up an Islamic state.

The president also told parents of the schoolgirls kidnapped from Chibok, in northeast Borno state, that their children would be freed. Since the girls were taken, Boko Haram fighters have killed at least 500 civilians, according to a Reuters count.

Nigeria has struck a deal with Niger to allow its troops to cross the border in pursuit of Boko Haram, and is discussing a similar deal with Chad, but it complains Cameroon's Far North region is being used by Boko Haram militants as a rear base.

Lieutenant Colonel Didier Badjeck, Cameroon's defence ministry spokesman, said on Tuesday on Tuesday the country had been timid with its response to Boko Haram due to lack of resources but had recently boosted troop levels in the region.

Cameroon has seen some Boko Haram attacks on its soil. Two weeks ago suspected Boko Haram rebels from Nigeria attacked a Chinese work site in northern Cameroon, killing at least one Cameroonian soldier and apparently abducting 10 Chinese workers.

Bello said such poor cooperation was a problem globally. "The jihadists are more global in their thinking than we are. We're still leaving it to individual nations," he said. "As long as we keep that approach, I can't see it working."