NIAMEY, Niger (AP) _ Boko Haram staged an overnight assault on a border town in Niger and a suicide bomber detonated explosives near a market in the same town a few hours later, witnesses said Sunday, in a sign the extremists' offensive against the West African nation was intensifying.

The attack on the town of Diffa began Saturday night, and fighting between Boko Haram and Niger's army lasted until 5 a.m. toward the town's southern entrance before the extremists were forced to flee and calm was restored, Diffa resident Adam Boukar said.

It was the second time the town had come under attack by Boko Haram since Friday.

A few hours after the attack was repulsed, a suicide bomber who witnesses said they believed was female blew herself up in Diffa's pepper market, which attracts traders and customers from Nigeria and other countries in the region.

``This young girl who was wearing the bomb made it explode right in the middle of the market. At the moment the market is surrounded by soldiers, and the rest of the town also,'' said resident Kader Lawan.

Officials could not immediately be reached to confirm residents' accounts or give casualty figures.

Boko Haram has used suicide bombers driving explosive-laden cars and wearing explosive vests in dozens of deadly attacks on crowded markets and bustling bus stations that have killed hundreds of people. This would be the first such attack outside of Nigeria.

The fight against Boko Haram has taken on an increasingly regional dimension in recent months, with the extremists staging attacks in both Cameroon and Niger last week alone. Foreign fighters from neighboring countries are said to be part of the terror group, which recruits with payments and by force as well as on an ideological basis.

On Saturday, regional and African Union officials meeting in Cameroon's capital, Yaounde, unveiled a proposal for a force of as many as 8,750 members to combat Boko Haram, with manpower coming from Nigeria, Chad, Cameroon, Niger and Benin.

Officials said they envisioned deploying the force as early as next month, though funding issues could delay that timeline.