Burundi's police on Sunday denied that it had summarily executed at least 22 members of a former rebel group, saying they had died during clashes between security forces and armed groups.

"It is not the first time the president of the Association for the Protection of Detainees and Human Rights has made accusations which are totally false," said Pierre Chanel Ntarabaganyi, a police spokesman.

The president of the rights group, Pierre Claver Mbonimpa, said on Saturday that at least 22 militants of the National Liberation Forces (FNL) had been summarily executed by agents acting for the police or intelligence services.

The FNL joined the government last year, but its leader Agathon Rwasa fled after local polls in May which the opposition accused the government of rigging.

"Small groups travel around and loot, kill and rape, and when police face these groups, there are exchanges of fire and sometimes police are killed or their people," the spokesman said.

"When these small groups invade a small village, they kill systematically... The police must use force to pursue them and it is normal that there are deaths," he said.

Renewed violence in Burundi in the past few weeks has left more than 30 dead, amid fears that new pockets of rebellion are growing in the country.

Authorities say they suspect two opposition groups whose leaders have gone into hiding of being behind the attacks, while other opposition parties say President Pierre Nkurunziza's government is becoming intolerant. 

Burundi has only just emerged from a 13-year civil war that left more than 300,000 dead.

(Source: AFP)