(Adds comment from official and Houthi spokesman)
SANAA, March 22 (Reuters) - Two Shi'ite Muslim Houthi tribal fighters and a soldier were killed in Yemen on Saturday in renewed clashes in the northern province of Amran, local officials told Reuters.
Elsewhere disgruntled tribesmen bombed Yemen's main crude export pipeline, forcing oil flows to be stopped. Attacks on oil and gas pipelines as a means to pressure the government are frequent in Yemen, causing fuel shortages and slashing export earnings for the impoverished country.
A group of armed Houthi fighters marched to the city of Amran early on Saturday and demanded to be allowed to stage a demonstration, but fighting broke out when the army refused to let them enter the city, an official in Amran told Reuters.
Last week, Houthis managed to hold an anti-government protest in Amran.
"The Houthis have staged these protests fully armed, that's why the army forces had to stop them from entering the city this time," said an official.
A source from Yemen's ministry of interior told state news agency SABA that the rebels attacked security checkpoints, leading to the death of one soldier and wounding two others.
"These armed outlaw elements belong to a subsidiary of Ansar Allah [a Houthi movement], they attacked a number of security points and tried to enter the city of Amran with various light and medium weapons," said the source.
Mohmed Abdel Salam, a Houthi spokesman, put the death toll among rebels at six. In a post on his Facebook page, he said shots were fired at protesters before they reached the security checkpoints.
"Once the march reached the checkpoint, there was direct shooting which led to the killing of six and the wounding of ten. Four others were arrested," Abdel Salam said.
Fighters loyal to the Shi'ite Houthi tribe, who have repeatedly fought government forces since 2004, are trying to tighten their grip on the north as Yemen moves towards a federal system that gives more power to regional authorities.
Last week at least 40 people were killed in clashes between Houthis and Sunni Muslim tribesmen near Sanaa.
Mediators have been trying to persuade the warring parties to retreat from their positions, which would be taken by government soldiers, but so far without success.
Gulf Arab states and the United States are concerned about violence in the Western-allied country as it is home to a wing of al Qaeda, shares a long border with top oil exporter Saudi Arabia and its coast runs alongside major shipping lanes. (Reporting by Mohamed Ghobari; Writing by Amena Bakr; Editing by Rosalind Russell)