Democratic Republic of Congo police killed at least 55 people in a crackdown on a separatist religious sect in April, more than double the toll reported by the interior ministry at the time, Human Rights Watch said on Tuesday.

New York-based HRW accused Congo authorities of using “excessive force" in dealing with the Bundu dia Kongo (BDK) group, whose leader had urged followers to chase other ethnic groups out of their core area of support in the country's west.

"Congolese authorities had a responsibility to respond to the BDK movement's messages that incite ethnic hatred," said Lewis Mudge, Central Africa director at HRW.

"However, the government response violated international standards on the use of force, causing a bloodbath," he said in an HRW report on the incidents in April.

"The government needs to get to the bottom of these violent raids and hold wrongdoers to account, whatever their rank."

In April, the interior ministry said police had killed 22 BDK members in two raids, one of which led to the arrest of BDK leader Ne Muanda Nsemi at his home in the capital Kinshasa.

But HRW's report said 55 were killed and dozens wounded during those raids and several other incidents, citing more than 50 interviews conducted with victims, witnesses, BDK members, government and U.N. officials.

Interior Minister Gilbert Kankonde did not immediately respond to Reuters' request for comment.

Quoted in Tuesday's report, he told HRW that investigations were ongoing into the April 22 police raid on a house containing BDK supporters in Songololo in Kongo-Central province.

Nsemi, a self-styled prophet and ex-member of parliament, had a strong following in the west of the country where he hoped to restore the Kongo kingdom that thrived around the mouth of the Congo River for centuries before the colonial era.

Nsemi was previously arrested in March 2017 after leading violent protests against then-President Joseph Kabila, only to escape prison with the help of supporters two months later.