French president François Hollande called the hardline group a “major threat to West and Central Africa”, and said it had links with al-Qaeda’s North African arm and “other terrorist organisations”.
He said regional powers had pledged to share intelligence and co-ordinate action against the group and France would assist by monitoring borders and co-ordinating action, including possible operations involving French troops.
President Idriss Deby of Chad said regional powers would “tackle this situation head on” and wage “total war on Boko Haram”.
Britain also offered to send advisers to help the Nigerian military organise its response to the rebels, who threaten to destabilise the wider region. Foreign Secretary William Hague, speaking just before the start of a meeting, said the Nigerian military was not yet able to deal effectively with Boko Haram.
The summit follows an attack on a Chinese construction camp in Cameroon on Friday night which resulted in the kidnap of at least ten people.
Although Boko Haram has been fighting for five years, carrying out bombings and attacks on civilians as well as security forces, the kidnapping last month of more than 200 girls from a school in Chibok, north-east Nigeria, has focused world attention.
The girls, who include Christians and Muslims, were seized on 14 April from their school hostel and face sexual abuse and rape if they refuse to convert to Islam and marry Boko Haram fighters.
Nigerian president Goodluck Jonathan has ruled out negotiations for their release.
Outrage over the mass abduction prompted Jonathan – criticised at home for his government’s slow response – to accept American, British and French intelligence help in the hunt for the girls.
France – itself a target of Islamist militants for its military intervention against rebels in Mali – brought together Nigeria’s neighbours Chad, Cameroon, Niger and Benin, and western officials to try to improve co-operation.
Boko Haram fighters have struck across borders on a number of occasions.
“Nigerian security forces have not been well-structured for this kind of thing and that has been shown by the problem getting worse,” Hague said. “We can help with that, which is why we are offering to embed military advisers within the Nigerian headquarters.”
But Nigeria must still lead the way, he emphasised.
“Nigeria has the main responsibility and must be the lead nation in tackling this and that includes to mount an effective security response and improve development,” he said.
With about 6,000 French troops operating in either Mali to the north-west or the Central African Republic to the east, Paris has a big interest in preventing a worsening of security in Nigeria.
It fears Boko Haram could spread north into the Sahel and beyond Cameroon into the Central African Republic.
“Boko Haram is a major threat for all of western Africa and now central Africa with proven links to Aqim (al-Qaeda in the Islamic Maghreb) and other terrorist organisations,” Hollande said.
“A comprehensive plan needs to be put in place from exchanging information to co-ordinating action and controlling borders,” he added.
Boko Haram has killed more than 3,000 people in its war to establish an Islamic state in mostly Muslim north-east Nigeria.
Nigeria has complained the far north of Cameroon is being used by militants to shelter from a Nigerian military offensive and to transport weapons, and has urged Cameroon to tighten border security.
“The first focus is about the girls, but that requires these countries work together particularly Cameroon and Nigeria who have not enjoyed strong, positive relations in recent years,” Hague said.