Yemeni tribesmen blew up a pipeline in the eastern Hadramout province on Saturday, disrupting oil flow two days after they seized an Oil Ministry building in the region, a local government official said.
The authorities face regular challenges from tribesmen who attack oil pipelines and power lines for reasons including demands for more employment and the release of jailed relatives.
Tribal sources said on Thursday that the Oil Ministry attack was in response to the killing of a tribal leader this month at an army checkpoint after his bodyguards refused to hand over their weapons to soldiers.
The pipeline attacked transports crude oil from Massila oil field in Hadramout to the port of Mukkala. This was the first time the pipeline has been hit.
Yemen, one of the Arab world's poorest countries, is struggling to restore state authority after long-serving President Ali Abdullah Saleh was forced to step down in 2011.
Four people were killed on Saturday and dozens wounded during clashes between security forces and armed secessionists in the southern Dalea province, medics and witnesses said.
The clashes came after an explosive shell hit a funeral gathering attended by southern separatists on Friday, killing 15 people, including children.
Yemen's north and its once-Marxist south united in 1990, but civil war broke out four years later. Then-President Saleh crushed southern secessionists and maintained the union.
President Abd-Rabbu Mansour Hadi has set up a committee to investigate the shelling, state news agency SABA reported.