By Abdoulaye Massalaki
NIAMEY (Reuters) - Niger troops and Chadian war planes fought off an attack on Friday on the Niger town of Bosso by Boko Haram militants whose insurgency is spreading from Nigeria to neighboring states, military officials in Niger said.
The fighting took place in the southeastern region of Diffa, part of the border area where Chad has sent hundreds of troops to help Niger take on Boko Haram, the sources said.
"The Boko Haram attack from Malam Fatori (in Nigeria) against the town of Bosso and the bridge at Doutchi in the Diffa region has been repulsed. We have Chadian planes bombarding the locality," said a Niger military source.
A second source said: "There is heavy weapons fire from both sides .... We have at least five injured in our ranks." Later a military source said the attack had failed, calm had returned and there was no hot pursuit operation into Nigeria.
Boko Haram has seized territory in northeastern Nigeria as part of a five-year insurgency for an Islamist state. Around 10,000 people were killed last year and the militants increasingly stage cross border attacks.
The insurgency is the worst threat to Nigeria's 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 neighboring 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 neighboring 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.
(Writing by Bate Felix and Matthew Mpoke Bigg; Editing by Louise Ireland)