HRW on Tuesday had said "government forces and armed ethnic Fulani" carried out the slaughter, which occurred on February 14 in a region where troops are battling anglophone separatists.

"The government totally rejects the allegations contained in this report," spokesman Rene Emmanuel Sadi, who is also minister of communication, said in a statement.

He said HRW, like other non-governmental organisations, had "rushed to publish an incorrect toll about this regrettable incident," even though an inquiry had been ordered by President Paul Biya.

The state TV channel CRTV, quoting the governor of Northwest Region, Adolphe Lele Lafrique, said Biya had given investigators "a week" to finish the investigation. It did not give the starting date of the inquiry.

HRW said 13 children and a pregnant women were among those killed in Ngarbuh, a district of Ntumbo village in Northwest Region.

Between 10 and 10 and 15 soldiers, including members of the elite Rapid Intervention Battalion, along with at least 30 armed Fulani, also called Peul, carried out the attack, it said.

After news of casualties emerged, opposition figures in Cameroon swiftly accused the armed forces of having played a role.

But on February 17, army spokesman Colonel Cyrille Atonfack Guemo said the deaths had resulted from an "unfortunate accident" when fuel was set ablaze during a gunfight between troops and separatists after a patrol came under heavy fire.

Five civilians -- a woman and four children -- had died, and "seven terrorists" were "neutralised," Atonfack told AFP.

The following day, the UN said 23 had died and urged Cameroon to carry out an "independent, impartial and thorough" inquiry.

HRW "has no material proof capable of supporting its claims," Sadi said on Friday.

The watchdog says its report is based on interviews with 25 people, including three witnesses to killings and seven relatives of victims, and on satellite imagery taken before and after the attack.

English-speakers account for nearly a fifth of Cameroon's population of 24 million, who are majority French-speaking.

Most of this minority live in two western regions called the Northwest and Southwest, which were once part of British colonies in West Africa.

Decades of grievances at perceived discrimination brewed into a declaration of independence in October 2017, which was followed by a government crackdown.

The declaration has not been recognised internationally and President Paul Biya, in power for 37 of his 87 years, has refused demands to return to a federal system.

More than 3,000 people have died and at least 700,000 have fled their homes. Rights monitors say abuses have been committed by both sides.