Two Hutu women were dragged out of a minibus, lynched and their bodies set on fire by a crowd in eastern Congo, the local mayor said on Wednesday, as inter-ethnic tensions in the region surge in the wake of massacres that have killed hundreds of civilians.

The crowd in the town of Butembo, which is dominated by members of the Nande ethnic group, said the two ethnic Hutu women who were traveling by minibus in North Kivu province were militants, mayor Sikuli Uvasaka Makala told local radio.

Dozens have died in tit-for-tat killings by ethnic militia this year.

Ethnic rivalries, invasions by Rwanda and Uganda and competition for land and minerals among eastern Congo's dozens of rebel groups have stoked conflict over the last two decades.

"I condemn the death of these two women," Uvasaka said. "I insist: stop carrying out popular justice. Do you want to put the Nande community at risk?"

Migration by Hutu farmers from North Kivu through predominantly Nande areas towards Ituri province in search of more fertile land has fueled tensions, Otto Bahizi, a Hutu tribal leader from nearby Rutshuru territory, told Reuters.

The government blames the massacres over the last two years that have killed more than 700 civilians on Ugandan Islamist rebels but independent analysts say other armed groups are involved and ethnic rivalries likely play a role.

About 50 civilians were hacked to death this month outside Beni, some 50 km (30 miles) north of Butembo.

Hundreds of young demonstrators again took to the streets of Butembo on Wednesday to protest against the government's failure to stop the killings. The army fired into the air and arrested about 15 people, a Reuters witness said.