Nigeria and neighbours form new force to fight Boko Haram
Nigeria and three other states have pledged to speed up the creation of a 2,800-strong regional force to tackle militant Islamist group Boko Haram.
Defence ministers of Nigeria, Cameroon, Chad and Niger said they would each contribute 700 troops to the force.
Niger's Defence Minister Karidio Mahamadou said they were determined to "eradicate this curse".
Boko Haram's insurgency is focused on Nigeria, but it has carried out some cross-border raids.
It was suspected of blowing up the Ngala bridge, which lies on a key transport link between north-eastern Nigeria and Cameroon, on Wednesday.
Cars and lorries loaded with goods are stranded on the highway, residents told the BBC.
The regional defence ministers met in Niger's capital, Niamey, on Wednesday, to hold further discussions on the growing threat posed by Boko Haram.
In May, the four countries, whose borders meet at Lake Chad, agreed to share intelligence and coordinate border security.
Efforts to step up regional co-operation gained momentum after Boko Haram caused an international outcry by abducting more than 200 girls from a boarding school in north-eastern Nigeria.
The girls are said to be held in the vast Sambisa forest, along Nigeria's border with Cameroon.
Boko Haram has carried out a spate of abductions in Cameroon - including that of tourists and priests.
Unconfirmed reports say the group has also recruited fighters from Chad and Niger.
On Wednesday, at least 40 people were killed when two bombs exploded in the northern Nigerian city of Kaduna.
Boko Haram has not commented, but it is suspected to have carried out the attacks.
It launched an insurgency in 2009 to create an Islamic state in Nigeria.