Niger's forces killed 109 fighters from the Islamist militant group Boko Haram on Friday as they repulsed attacks on Bosso and Diffa, two southeastern towns near the Nigerian border, Niger state television said.

Four Niger soldiers were killed, 13 were wounded and two are missing after the fighting in Bosso against Boko Haram, whose five-year insurgency is spreading from Nigeria to neighbouring states. Four Niger soldiers were wounded in Diffa.

"At around 9 am elements of the Boko Haram terrorist group launched two simultaneous attacks at Bosso and Diffa. At Bosso, Niger's defence forces helped by Chadian troops neutralised the assailants," said the statement by Defence Minister Karidio Mahamadou on state television.

Chad deployed war planes to repulse the attack, military officials in Niger said earlier.

There was no independent confirmation of the numbers killed.

General Yaya Doud, commander of Chadian forces deployed north of Lake Chad, was shot in the stomach in Bosso, a Chadian security source said. He has been evacuated to hospital in N'Djamena for treatment.

"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.

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 February 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.