At least 48 people have been killed in clashes between rival Arab nomadic groups in Sudan's Darfur region, says a Misseriya clan leader quoted by the BBC.
He said Rezeigat fighters in cars had stormed villages on Friday morning and the fighting had continued until sunset.
The Rezeigat and Misseriya and have been caught up in a series of revenge attacks in West Darfur since February, the BBC said.
A spokesman for the joint African Union and UN peace force said a team had been sent to investigate the reports.
"Tribes were blocking some of the access routes to where the fighting was reportedly going on," spokesman Chris Cycmanick told Reuters news agency.
"The local population told us 40 were killed and 10 were injured."
Correspondents told BBC there are often clashes about grazing rights for cattle and water sources in the area.
"Members of the Rezeigat tribe riding in nine vehicles... attacked three of our villages on Friday," Misseriya leader Ezzedine Eissa al-Mandil told AFP news agency, according to BBC.
Mandil told Reuters that 21 Misseriya had been killed and 27 from the rival Rezeigat group had died in the clashes near the settlement of Garsila in West Darfur, BBC said.
The violence coincides with an upsurge in fighting between the government and the rebel Justice and Equality Movement.
About 600 people died in fighting in Darfur last month - the highest monthly toll since UN and AU peacekeepers were deployed in 2008, BBC said.