Police in the Democratic Republic of the Congo (DRC) have revised downwards the number of police officers it says were massacred in the restive Kasaï-Central province on 24 March.

Kasaï, in the heart of the DRC, has been plagued by violence between the Congolese security forces and a local militia, Kamuina Nsapu, who are seeking to avenge the death of their leader, Kamuina Nsapu, in August 2016.

Police officials in Kananga were initially quoted as telling the UN Peacekeeping mission to DRC (Monusco) that six policemen had managed to flee but 42 policemen were killed by suspected Kamuina Nsapu fighters in Kasai province on Friday.

Other sources quoted by UN-funded Radio Okapi, claimed up to 52 policemen were beheaded in the attack.

On 27 March, however, Colonel Pierrot Mwana Mputu, spokesman of the Congolese National Police (PNC), confirmed 39 policemen were killed in the ambush when militiamen, armed with machetes, raided the officers' convoy that was travelling from Tshikapa to the province's capital, Kananga.

In his public statement, Mwana Mputu gave some new, harrowing details about the attack: two police trucks were stopped in the village of Kamuesha, less than 80 kilometres from the town of Tshikapa.

All the victims were buried in a mass grave dug on the very spot of the ambush. The spokesman added that the attackers drove away the police trucks, and stole all the police equipment aboard.

"In addition to the 39 officers killed, the report also shows two police trucks for the transport of troops removed with a large cargo of police equipment and materials," Mwana Mputu said.

The PNC condemned "this massacre and wishes to reassure the public that the urgent and consequent measures have been taken to put a definitive end to the insecurity that prevails in this part of the Republic, to stop these sociopaths [and ensure] the return of peace among the population."

The provincial administration said it has launched a probe into the killings and vowed to punish the perpetrators.

This comes as a global human rights umbrella organisation, FIDH, on 27 March urged the UN Security Council to renew Monusco's mandate amid a continuing deterioration of the security situation in the country.

Monusco said on 18 March it is concerned by the attacks of Kamuina Nsapu militiamen against State institutions and symbols, and warned of the disproportionate use of force by the security and defence forces and the targeting of civilians, including women and children.

Following the recent discovery of three mass burial sites, UN High Commissioner for Human Rights Zeid Ra'ad al-Hussein on 8 March called for a high-level investigation into "grave" violations committed against civilians in the region. DRC's government spokesman Lambert Mende said that a Congolese judicial investigation was under way.