Authorities in the Democratic Republic of Congo must protect civilians from rival Bantu and Pygmy fighters in a conflict that has killed hundreds since 2013, Human Rights Watch said Tuesday.

"The widespread killing and displacement of civilians" in northern Katanga province "show the urgent need" for government protection, the New York-based HRW said in a report.

Fighting broke out two years ago between a tribe of the Bantu majority, the Luba, and Pygmies from the Batwa group, who consider that they have long been marginalised, exploited and despised.

Raids on settlements and clashes between opposing forces, armed mainly with machetes and bows and arrows, have frequently led to massacres, looting and the burning of villages in the southeastern province.

"Simmering tensions between Batwa and Luba in Katanga erupted in major fighting in mid-2013 in Manono territory, after Batwa started demanding respect for their basic rights, including access to land and an end to alleged forced labour or a form of slavery," HRW said on the strength of missions from May to July.

The Pygmies are a hunter-gatherer people with a deep lore of nature who have lived for generations mainly in the bush and tropical forests of DR Congo, the Republic of Congo, the Central African Republic, Cameroon and Gabon.

In DR Congo, their millennial lifestyle is threatened by deforestation and the spread of Bantu farming communities, along with mining of the country's vast mineral resources.

Large-scale clashes have spread and the UN mission in DR Congo, MONUSCO, has reported hundreds of civilians slain, tens of thousands displaced and dozens of villages razed.

"Protecting civilians from all communities who are at grave risk needs to be the government's priority in northern Katanga," said HRW's senior Africa researcher, Ida Sawyer.

"But the issues underlying the violence won't be resolved so long as the basic rights of the long-oppressed Batwa are not respected," he added after HRW spoke to victims, Congolese authorities and security forces, aid workers and UN peacekeepers.

- 'Treated as sub-humans' -

During "one of the worst recent incidents" on April 30, Luba militias attacked the Vumilia 1 camp for displaced people - mainly Batwa - near Nyunzu town, reducing it to ashes and killing "at least 30 men, women and children," HRW said. Dozens more went missing, feared dead.

"Local and provincial government and army officials - many of whom are Luba - sought to minimalise the Vumilia 1 killings. Without backing up their claims, they said the number of Batwa killed ranged from none to four," the report said.

The attack on the camp came in the wake of brutal raids by Pygmies against Luba in the first months of 2015, according to witnesses and other sources interviewed by HRW.

The UN Office for the Coordination of Humanitarian Affairs (OCHA) has noted that while the Luba tended to attack Batwa in 2014, roles have often reversed in 2015. Official calls for peace have failed to stop the violence and mass displacement.

Provincial Interior Minister Juvenal Kitungwa acknowledged to HRW that ending underlying discrimination against Batwa people is a key to resolving the violence.

"The Pygmies felt like they were living under an apartheid situation. This conflict won't end today or tomorrow. It's a movement for the emancipation of a people," Kitungwa said on July 10.

"One of the solutions will be in improving access to education and access to land for the Pygmies," he added, noting that as the Batwa were forced out of their accustomed homes into settlements, "it's like they're now treated as sub-humans who are forced to work for the Luba."