NIAMEY, Niger — Nigeria's Islamic extremists invaded a second country in the region Friday, attacking two towns in a part of Niger that is already home to tens of thousands of refugees who have fled the terror group's attacks back in Nigeria.
The expansion of Boko Haram's reach came as neighboring countries are fighting back with ground troops and aircraft, with even greater military strikes by more countries planned. The U.S. strongly condemned the Boko Haram attacks and pledged continuing assistance to fight the militants.
Boko Haram has openly threatened to attack other countries taking part in the military effort to subdue their insurgency, blamed for 10,000 deaths over the past year. Cameroon, Niger, Chad and Benin all have pledged to send troops to fight Boko Haram, which has waged a five-year rebellion against the Nigerian government.
On Friday, soldiers from Niger and Chad fought an hour-long battle that caused Boko Haram fighters to withdraw from Bosso, leaving the Niger town's streets deserted, said Abba Hassan, a local pharmacist.
"Niger and Chadian planes are conducting surveillance at the moment in town and troops on the ground are combing through the streets," Hassan told The Associated Press by phone.
There was no immediate word on casualties, and Niger's government spokesman could not immediately be reached for comment. Niger's president was holding a Cabinet meeting Friday.
The area of Niger where the attack took place is flooded with Nigerian refugees who have fled Boko Haram's violence in Nigeria. Niger's government cites 100,000 displaced people, making one out of six in the region a refugee.
Those fleeing the violence in Bosso were headed toward Diffa, a second town hit by Boko Haram fire on Friday. At least four mortar rounds fell in the town though there were no immediate reports of injuries, according to an aid official in the capital who had spoken with witnesses. The official spoke on condition of anonymity as he was not authorized to speak to the media.
Friday's violence in Niger also followed a Jan. 31 message in which Boko Haram fighters vowed to seek revenge if Niger aided the effort against the terror group.
"Their government is leading them into a dark tunnel if it joins a coalition with Chad and Cameroon against us, that it will use their sons in a war in which they have nothing to gain but fighting against Allah and His messenger," said a transcript released by SITE intelligence monitoring service.
On Wednesday and Thursday, Boko Haram fighters attacked Fotokol, in Cameroon, leaving nearly 100 people dead and some 500 wounded, according to Cameroonian officials. The extremists razed mosques and churches and used civilians as human shields before Cameroonian forces pushed them back across the border to Nigeria.
"Cameroonian soldiers assisted by Chadian forces have successfully chased hundreds of Boko Haram fighters out of the Cameroonian locality of Fotokol on the border with Nigeria," said Cameroon government spokesman Issa Tchiroma Bakary.
The cross-border assaults came after Boko Haram was bombed out of several Nigerian towns earlier this week by Nigerian and Chadian jets. Cameroon and Chad joined Nigeria in launching an air and ground offensive against the insurgents on at least two fronts this week.
Regional leaders were meeting Friday for a second day in Cameroon's capital, Yaounde, to finalize plans for a coordinated military response.
Last week, leaders of the African Union authorized a 7,500-strong force to fight Boko Haram, including pledges of troops from Nigeria and four neighboring countries, Cameroon, Chad, Niger and Benin. The United Nations have offered logistical support. The deployment of the multinational African force could be delayed by funding issues.
French President Francois Hollande has said that France was supporting the operation with flights over the area to provide intelligence, as well as supporting with logistics, fuel and munitions, though he stopped short of saying whether France would participate in military action. France has a big air base in N'Djamena, the capital of Chad, which will lead the multinational force. N'Djamena lies on the eastern edge of Cameroon's panhandle, near the conflict zone.
The U.S. State Department condemned the "recent terrorist attacks by Boko Haram in Cameroon and Niger in the strongest possible terms," spokeswoman Marie Harf said Friday, adding that the group's "brutality and barbarism know no bounds."
The United States pledged to "continue to provide support to governments in the region, including through intelligence sharing" to help make the multinational African effort against Boko Haram "an effective force."
Larson reported from Dakar, Senegal. Associated Press writers Edwin Kindzeka Moki in Yaounde, Cameroon and Michelle Faul in Dakar, Senegal contributed to this report.