At least 38 people were killed on Sunday in clashes between rebel forces and tribes near a southern oil region, a security official and tribal sources said.
The fighting erupted when tribesmen attacked positions held by Huthi rebels near the oil-rich area of Usaylan in Shabwa province, the sources said.
"The Huthis and their allies (troops loyal to ex-strongman Ali Abdullah Saleh) have lost 30 of their men in fighting that killed eight tribesmen," the security official said.
Tribal sources confirmed the toll.
The clashes come as Saudi-led coalition warplanes pound rebel positions across Yemen in a four-day-old campaign to try to prevent the fall of President Abedrabbo Mansour Hadi.
Arab coalition warplanes later on Saturday shelled a road between Shabwa and Baida provinces, in an attempt to cut off Huthi supply lines, tribal sources said.
Sunni tribes in the nearby province of Abyan also sent 200 vehicles loaded with arms to reinforce tribesmen in Shabwa, the sources said.