By Aaron Ross

KINSHASA (Reuters) - Police in southwestern Democratic Republic of Congo on Friday killed at least eight members of a separatist religious sect, local activists said, escalating tensions in a normally peaceful part of a conflict-ravaged country.

The police opened fire on members of Bundu dia Kongo (BDK) as they approached the morgue in the town of Kimpese to recover the bodies of fellow members killed in protests last month, Jonas Lukoki, the provincial coordinator of the New Civil Society, told Reuters.

"There were 12 deaths, including three children," Lukoki said. Another local activist in Kimpese said that the police had killed at least eight BDK members. Both activists said the demonstrators were unarmed.

A police spokesman told Reuters that several people had been killed when BDK members clashed with the police in Kimpese but did not have further details.

Analysts say President Joseph Kabila's failure to step down when his constitutional mandate expired in December has led to a surge in activity from multiple armed groups, often with deadly consequences.

Armed clashes used to be rare in western Congo, unlike the east, where dozens of rebel groups and militia operate. But violence has increased there in recent months, including clashes in December between another religious sect and security forces in the northwest that killed at least 18 people.

BDK was founded by self-proclaimed prophet Ne Muanda Nsemi in the 1980s. It seeks to revive the pre-colonial Kongo kingdom, which flourished for centuries around the mouth of the Congo river at central Africa's Atlantic coast.

Security forces killed more than 300 of its members and bystanders in crackdowns on sometimes violent protests in 2007 and 2008, rights groups say. It claims to have thousands of supporters, but this number hasn't been verified.

The government said at the time it needed to assert its authority and went on to ban BDK in March 2008, but the group continues to command a significant following in the region.

(Editing by Tim Cocks, Larry King)