Witnesses say at least four people have been killed in a police clampdown on a separatist political and religious group in Congo's capital.

A police operation against members of the Bundu Dia Mayala movement at its founder's home left at least two members dead, according to witnesses.

Jean Onema Wembo, mayor of the Ngiri-Ngiri commune south of the capital, said two others were killed elsewhere in clashes between police and suspected members.

Police did not confirm the deaths but said at least 22 suspected members were arrested, and eight others were wounded in the raid.

Ne Mwanda Nsemi has led the sect since 1986. The group says it seeks the rehabilitation of the pre-colonial Kongo kingdom. Clashes between the sect and police in 2008 saw hundreds killed in Bas-Congo province.