With the Nigerian army struggling to contain the fighters, bordering countries have launched a major regional offensive against them, spurring a series of revenge attacks inside Niger and Cameroon.
Boko Haram members stormed a prison in the Niger town of Diffa overnight and set off a car bomb elsewhere in the town, witnesses said, shortly before Niger's parliament was due to ratify participation in the regional offensive — which would mean crossing borders.
Heavy gunfire carried on through the day as Niger's army repelled the assault, Boko Haram's third on Diffa in four days. A member of the national guard said about 100 suspected Boko Haram fighters were in prison in Niger, but none in Diffa.
"We will defeat Boko Haram. Boko Haram has no future in this region," Niger President Mahamadou Issoufou told reporters on Monday in the capital, Niamey.
Authorities ordered residents to stay in their homes, and had mounted roadblocks around Diffa by late morning. Residents and humanitarian officials said thousands of people were fleeing from the town in cars and on motorbikes.
In Cameroon, suspected Boko Haram fighters attacked the northern village of Kerawa on Sunday and kidnapped at least 18 people traveling on a bus near Adanga Danga, military sources said. One said there were 30 people on board the missing bus.
Military sources in the two countries said troops had killed at least a dozen of the group’s fighters in two days.
On Saturday, the governments of Cameroon, Chad, Niger, Nigeria and Benin agreed to establish an 8,700-strong multinational force to take on Boko Haram. Top U.S. military brass and the heads of 35 African armies discussed renewed security policies in Senegal on Monday at a conference, where Boko Haram featured prominently on the agenda.
Troops from Chad are already waging an offensive inside remote northeastern Nigerian territory and claim to have killed hundreds of Boko Haram fighters last week.
A video seen by Reuters on Monday appears to show Boko Haram leader Abubakar Shekau mocking the plans for a regional military intervention. "This message is for the people and leaders of Africa. You cannot defeat us ... Sit back and rethink. Is your constitution and democracy better than Islam?" he said in a 28-minute speech.
Shekau also directly threatened Chad's President Idriss Deby, whose forces have attacked Boko Haram in the northeast Nigerian towns of Gamboru and Malam Fatori in recent days.
Al Jazeera and wire services