Pygmy-Bantu clashes over a caterpillar collection tax have left 20 people dead in DR Congo and sparked fears of a new flare-up in trouble that over the past two years displaced tens of thousands of people.

Local MP Kalunga Mawazo told AFP on Tuesday that the fresh fighting was triggered by a dispute over the caterpillar harvest, a common food staple for the hunter-gatherer Pygmy people of the Tanganyika region in northern Katanga province.

"The attacks since Sunday left four (Bantu) Lubas and 16 Pygmies dead in a row over the tax traditionally paid to the Bantus by the Pygmies," Kalunga said.

A local priest who asked not to be named said that "the Pygmies believe they now have the same rights as citizens as the others. They refused to pay this illegal tax and shot two Luba people dead with arrows when they demanded payment."

Another two Lubas, who are Bantu people, were killed in revenge attacks. The bodies of 16 Pygmies were also found, the priest said.

Tanganyika governor Ngoy Kitangala said that security forces were being dispatched to the area where tension remains extremely high.

Pygmies from the local Twa group have long complained of being marginalised, exploited and despised by Bantu people living in farming communities, saying they treat them like second-class citizens.

- Love affair leads to war -

But it was a love affair between a Bantu and his Pygmy mistress that served as the trigger to repeated clashes between the two communities that broke out in 2013 in northern Katanga, a region as big as Spain.

"A Bantu was surprised in flagrante delicto of adultery with a Pygmy woman," a Bantu village chief told AFP at the time.

Due to the long simmering problems between the two peoples, the fighting in one of the world's poorest regions quickly degenerated, unleashing a cycle of revenge killings, looting and the burning of entire villages.

More than 200 people were reported dead in the 2014-2015 violence and tens of thousands fled fighting that pitted bows and arrows against machete blades.

Cohabitation has never been easy between the two communities, with the land-owning Bantus accused of exploiting the hunter-gatherers, paying them meagre wages, or paying them in alcohol and cigarettes for labouring the land.

For generations the Pygmies have wandered the bush and tropical forests of DR Congo, the Republic of Congo, the Central African Republic, Cameroon and Gabon.

But their millennial lifestyle is increasingly under threat from deforestation, mining and extensive farming.

Tension with the Bantu people had eased in recent months thanks to mediation efforts by local authorities and UN officials. But in September new clashes near the eastern town of Kabalo left eight dead.