Boko Haram is flush with cash and weapons after a string of battlefield advances, but the fighting group could face a tougher fight with Nigeria's neighbours, US intelligence officials have said.

In an assessment of the group, whose five-year uprising has included massacres and kidnappings and spread from Nigeria into neighboring states, the officials said they did not believe it posed a major threat to Nigeria's oilfields in the south.

They said the group has about 4,000-6,000 "hardcore" fighters - considerably less than some estimates which have put the group's size at up to 10,000.

The group is "financially secure" from bank robberies, kidnappings and other sources, and is able to go "toe-to-toe" with the Nigerian military after capturing an arsenal of arms, the intelligence officials told reporters.

However, the group could soon face an unprecedented test on the battlefield against more capable forces from Cameroon, Chad and Niger, they added.

The military intervention of neighbouring powers "potentially can be a game changer in a positive way," one intelligence official said.

Schoolgirls still held

The officials, who spoke on condition of anonymity, said Boko Haram were believed to be still holding about 300 schoolgirls they kidnapped early last year and had dispersed them to multiple locations.

Around 10,000 people were killed in Boko Haram attacks last year. The Sunni Muslim group poses the biggest security threat in Nigeria, Africa's top oil producer and biggest economy.

Concern over the insurgency appears to be and one of the main reasons for what appears to be a surge in political support for opposition leader Muhammadu Buhari in a February 14 election.

Many Nigerians believe Buhari, as a former military ruler, will be able to bolster the army's hapless efforts to counter the insurgency, and that as a Muslim he may even be able to take some of the wind out of Boko Haram's ideological sails.

The officials said the group had been engaging in both small-scale and larger attacks in recent weeks and they expected this mixed pattern of operations to continue during the election period.

The US officials' comments came as Boko Haram suffered heavy losses after launching a major attack into Niger on Friday for the first time.

The clashes involved troops from Niger as well as Chad, which has adopted a leading role in the fight against the group.

Source: Reuters And AFP