Cameroon, Chad and Niger have launched a regional bid to combat the Boko Haram Islamists, as their attacks spread beyond Nigeria and concern mounts over the Nigerians' failure to regain control.
The three neighbours have opted for a joint military response to the cross-border threat from Boko Haram fighters and have made veiled criticisms of Nigeria, whose armed forces appear no match for the Islamist group that emerged in 2009.
Brutal raids, massacres, suicide bomb attacks and kidnappings by Boko Haram have claimed at least 13,000 lives and driven an estimated 1.5 million people from their homes, mainly in arid northeast Nigeria.
Officially, all four states, whose borders converge in remote territory at Lake Chad, formed a military alliance that was due to take shape last November to battle Boko Haram.
But building a combined Lake Chad force seems to have dropped off the agenda.
Now the urgency of the situation is such that Nigeria's partners appear to have finally lost patience and decided to act.
Cameroon in particular has been critical of what it sees as the Nigerian authorities' passivity in the face of Boko Haram.
Yesterday, after Chad's parliament voted to send armed forces to Cameroon and Nigeria to help fight the Islamists, Chadian army vehicles headed south out of the capital N'Djamena.
The move comes after the Islamists seized Baga town on the Nigerian shore of Lake Chad early this month in an offensive that "could be Boko Haram's deadliest act", according to Daniel Eyre, Nigeria researcher for Amnesty International.
Satellite pictures released by Amnesty and Human Rights Watch last week showed widespread destruction with around 3,700 buildings in Baga and nearby Doron Baga damaged or destroyed.
Eyre said as many as 2,000 civilians may have been massacred, but Nigeria's army objected to the "sensational" claims and said that the death toll in Baga was about 150.
The Islamists detained "over 500 women and hundreds of children" in a school, one woman who escaped the area told AFP, adding that she had seen "decomposing bodies scattered all over".
US Secretary of State John Kerry on Thursday joined rights monitors in blaming Boko Haram for "a crime against humanity" on the basis of evidence from the towns in northern Nigeria.
Nigeria's army had planned to use the isolated settlement of Baga as one of its key bases to work with a regional force.
