By Joe Bavier

NIAMEY (Reuters) - A multinational force has begun operations against Boko Haram along the border between Niger and Nigeria, a general from Niger said on Tuesday.

Brigadier-General Abdou Sidikou Issa, tactical chief of staff for troops based in Niger's southern zone of Diffa, a region plagued by the Islamist militant group, said troops from Chad and Nigeria were involved in the operation. It began in secret almost a week ago.

This is not the first time the nations in the Lake Chad basin -- Niger, Nigeria, Chad and Cameroon -- have joined forces against Boko Haram, a violent Islamist group which started in Nigeria seven years ago and has since launched deadly attacks in all four countries.

"The operations have as their objective (to end) the occupation of all the zones currently occupied by Boko Haram," Issa said. "Our role is to firmly secure the border."

The multinational force, headquartered in Chad's capital of N'Djamena, began trying to dislodge the militants from areas where they are active last year.

Niger and Chad have performed joint army operations against Boko Haram, which wants to establish an Islamic state in West Africa, since early 2015.

Chad this month committed soldiers to the latest counter-attack against Boko Haram after its fighters attacked the southern Niger town of Bosso, killing 26 soldiers.

(Writing by Makini Brice; Editing by Tim Cocks and Gareth Jones)