Clashes between rival Arab groups killed 48 people in Sudan's Darfur region, a tribal leader said on Saturday.
International peacekeepers could not confirm the clashes but said they had received reports from locals of the fighting north of the settlement of Garsila in West Darfur state on Friday.
Some Arab leaders and UN officials have said the rival Rizeigat and Misseriya tribes are caught in a cycle of revenge attacks dating back to the killing of two members of the Misseriya tribe in February or March.
Last week one UN source, speaking on condition of anonymity, said there was also an underlying struggle for control of fertile grazing land.
The violence has coincided with an increase in fighting between Sudanese government troops and members of Darfur's rebel Justice and Equality Movement (JEM).
Tribal violence and a breakdown in law and order have complicated the Darfur conflict, which broke out in 2003 when mostly non-Arab rebels took up arms accusing Khartoum of marginalising the region.
"Yesterday at morning, forces from Rizeigat tribe using nine Land Cruiser cars, attacked the Misseriya village of Kankulay, north of Garsila in West Darfur state," Misseriya leader Ezzedin Eissa al-Mandil told Reuters on Saturday.
"The fighting continued from morning until sunset. It continued all the day."
He said the fighting killed 21 members of the Misseriya tribe and 27 from the Rizeigat. No one from the Rizeigat was immediately available for comment.
Darfur's joint UN African Union UNAMID peacekeepers sent a team to the area on Saturday, said spokesman Chris Cycmanick.
"Tribes were blocking some of the access routes to where the fighting was reportedly going on. The local population told us 40 were killed and 10 were injured," he said.
Darfur's conflict has rumbled on despite years of diplomatic pressure from Washington and high-profile campaigns by celebrities and activists.
UNAMID head Ibrahim Gambari told the UN Security Council this week 447 people died in Darfur in May in what he called a "serious escalation" in violence, that has also disrupted aid work across the region.
Estimates of the total death count from the seven-year conflict range from 300,000, according to the UN's humanitarian aid chief John Holmes, to 10,000, according to the Sudanese government.
