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.