Boko Haram fighters on Friday attacked a military base in eastern part of Niger Republic, expanding its reign of terror across the region, witnesses said.
It is the first time the Nigeria-based insurgents launched an assault in Niger Republic, after infiltrating northern Cameroon for the past few months, killing dozens of people.
Boko Haram clashed with soldiers in Bosso, a town that borders neighbouring Nigeria.
However, a causality figure could not be confirmed.
The attack came a day after Boko Haram killed 31 people in northern Cameroon, when it burnt three mosques in the town of Fotokol, also near the Nigerian border.
Insurgents on Wednesday killed 82 civilians in Fotokol, as well as six Cameroonian and 13 Chadian soldiers.
Boko Haram descended on Fotokol in apparent retaliation for the deaths of over 200 of their members killed this week by Chadian and Nigerian troops.
Nigerian and Chadian aircraft have been bombing Boko Haram hideouts since Monday.
No fewer than 2,000 Chadian soldiers were stationed this week along the Nigeria-Cameroon border after the AU agreed on Jan. 31 to send 7,500 troops to fight Boko Haram.
Boko Haram has killed over 13,000 people since 2009 in northern Nigeria under the pretext of trying to establish an Islamist state.
The insurgents control about 130 villages and towns in northern Nigeria, a territory the size of Belgium, and have sparked fears of regional instability.