By Aaron Ross

BENI, Democratic Republic of Congo, Oct 28 (Reuters) – U gandan rebels suspected of massacring at least 80 people in northeastern Democratic Republic of Congo this month have been depleted and are adopting new guerrilla tactics, the Congolese interior minister said on Tuesday.

Violence simmers in Congo’s rugged eastern borderlands more than a decade after the vast Central African nation’s last war formally ended in 2003. A push by U.N. peacekeepers and government troops to stamp out residual armed groups has made progress following the defeat of M23, the zone’s strongest insurgency, last year.

However, fighters believed to belong to the Islamist ADF-NALU attacked villages near the town of Beni in a series of overnight raids this month, hacking their victims to death with hatchets and machetes.

“We know they are weakened in numbers … Now they act in small groups using guerrilla tactics and rely on surprise,” Richard Muyej told Reuters in an interview on Tuesday.

“We are trying to redeploy our troops to try to combat their new strategy. It’s very early to say that we’ve succeeded. But we’re on the right path,” he said.

Muyej said that 45 suspects had been arrested in connection with the attacks.

President Joseph Kabila was due to visit Beni on Wednesday.

The Congolese army launched Operation Sukola against the ADF-NALU in January with the backing of the country’s U.N. mission, MONUSCO, forcing the rebels out of all their known bases, according to a June report by a panel of U.N. experts.

Estimates of their strength vary greatly, but MONUSCO’s website put their forces at around 500 fighters.

Muyej’s comments echoed those of Martin Kobler, the head of MONUSCO, who told the U.N. Security Council on Monday that operations in recent months had weakened the rebels and allowed tens of thousands of local residents to return to their homes.

Kobler warned, however, that a battered ADF-NALU could be using attacks on civilians to draw the Congolese army away from offensive operations.

The killings sparked anger in Beni last week as residents accused the U.N. soldiers of not doing enough to protect them. Crowds of mainly young men attacked several of the mission’s facilities in North Kivu province, throwing stones and forcing the evacuation of staff.

(Editing by Joe Bavier and Ralph Boulton)