Yemen tribal leader killed at opposition protest

* Tribal leader shot dead during protest in north

* Tribesmen prevent repair of pipeline in central Yemen

SANAA, March 15 (Reuters) - A Yemeni tribal leader was killed in clashes that broke out on Tuesday between protesters demanding the resignation of President Ali Abdullah Saleh and his supporters, a local official said.

Naji Nasm, who backed the Islamist opposition Islah (Reform) party, was shot dead during a demonstration in the northern al-Jawf province, the official told Reuters.

The impoverished Arabian Peninsula state has been rocked by weeks of demonstrations that have undermined Saleh's 32-year grip on power, with both pro- and anti-government factions appearing to resort increasingly to violence in the struggle.

At least eight demonstrators and three soldiers have died since Saturday, raising the death toll from unrest to almost 40.

The United States, which has long seen Saleh as a bulwark against a dynamic al Qaeda wing based in Yemen, has condemned the bloodshed and backed the right to peaceful protest. But it has also insisted only dialogue can end the political crisis.

In the central province of Maarib, tribesmen prevented technicians from repairing an oil pipeline that was damaged in an attack on Monday, officials told Reuters.