STR, Associated Press
In his file image taken from video released late Friday evening, Oct. 31, 2014, by Boko Haram, Abubakar Shekau, centre, the leader of Nigeria's Islamic extremist group. Boko Haram fighters have shot or burned to death about 90 civilians and wounded 500 in ongoing fighting in a Cameroonian border town near Nigeria, officials in Cameroon said Thursday, Feb. 5, 2015.

YAOUNDE, Cameroon — Nigeria's Islamic extremists Boko Haram pushed their conflict further into neighboring countries with attacks on Cameroon and Niger, abducting more than 30 people including those aboard a packed bus, said residents Monday.

Three Cameroonian towns were attacked and in Niger, the town of Diffa was attacked for the third time in recent days.

To battle Boko Haram, nearby countries have pledged to send troops to help Nigeria squash the militant group that killed more than 10,000 people last year. Nearly a year ago Boko Haram abducted more than 200 Nigerian schoolgirls who remain missing.

In northern Cameroon, the fighters seized a bus with 20 people aboard in Koza late Sunday and then drove it back toward the Nigerian border, some 11 miles (18 kilometers) away, resident Bouba Kaina told The Associated Press by telephone.

Early Monday, another Cameroonian town, Kolofata, was attacked by extremists who looted food and livestock. The town had recently been retaken by Chadian troops who have been helping Cameroon fight Boko Haram.

In Niger, Diffa was attacked overnight, the third attack since Friday on the town which has tens of thousands of refugees who have fled Boko Haram's attacks elsewhere. Calm had returned by Monday morning, but residents are rattled.

"Gunfire and heavy explosions were heard throughout the night until the early hours of the morning," said Adam Boukar, who runs a radio station in Diffa.

Diffa first came under assault Friday, as Boko Haram militants also besieged the town of Bosso. Then Saturday night, the fighters renewed their assault on Diffa with fighting that lasted until 5 a.m.

To mobilize a regional response to Boko Haram, officials from neighboring countries and the African Union met in Cameroon's capital, Yaounde, on Saturday and pledged to create a force of as many as 8,750 troops with soldiers from Nigeria, Chad, Cameroon, Niger and Benin. Chad is to command the force from its capital, N'Djamena. Officials said the force could be deployed as early as next month, though funding issues could delay its launch.

Boko Haram scoffed at the regional effort.

"You are sending 7,000 of your soldiers. Why don't you send 7 million? The 7,000 is little and we can kill them step by step ... your soldiers are infidels and God's soldiers are victorious," said Boko Haram leader Abubakar Shekau in a video posted on YouTube.

Shekau also told the people of Chad and Cameroon to renounce democracy to be true Muslims. He ridiculed the force planned by "you tyrants of Africa" and tells Chad's President Idriss Deby that he will "burn in hellfire."

Associated Press writers Dalatou Mamane in Niamey, Niger, and Maamoun Youssef in Cairo contributed to this report.