Niamey - Boko Haram militants clashed on Friday with soldiers in Niger, who were reinforcing border positions to fend off the insurgency that is spreading from Nigeria into neighbouring states, officials in Niger said.
At least five local soldiers were wounded, they said.
The fighting is taking place in the southeastern region of Diffa where Chad has sent hundreds of troops to help Niger take on Boko Haram at its long, porous border.
Violence erupted when Boko Haram fighters, who have seized swathes of territory in Nigeria, attacked the Niger town of Bosso from the neighbouring Nigerian town Malam Fatori, a military source said.
Also read: The origins of Boko Haram
Niger and Chadian troops were holding their positions in the town, he said.
A second source told Reuters by telephone, "There is heavy weapons fire from both sides. The fighting is intense and we have at least five injured in our ranks."
Boko Haram, which wants to set up an Islamic emirate in northern Nigeria, has emerged has the worst threat to Nigeria security as the nation, Africa's top oil producer and biggest economy, heads to a presidential election on Feb. 14.
The militants are also increasingly threatening neighbouring Chad, Niger and Cameroon, prompting regional leaders to come up with a joint plan to defeat them.
Chad has deployed some 2,500 soldiers to neighbouring Cameroon and Niger as part of this effort. Niger's parliament is due to vote on Monday on a proposal by the government to send its troops into Nigeria to fight Boko Haram.