RIYADH, April 10 (Reuters) - Unidentified gunmen have killed two Saudi border guards who were patrolling Saudi Arabia's border with Yemen, the Saudi state news agency said on Thursday.
The gunmen opened fire on a border patrol early on Wednesday in Dhahran al-Janoub in the southwestern province of Asir, SPA reported, but did not say who was behind the attack.
Saudi Arabia, wary of traffickers and militants trespassing from Yemen, has been building a security fence along its 1,800 km (1,100 mile) border with the impoverished country since 2003.
Work on the fence has often been halted by protesting Yemeni tribesmen, who say it prevents them from reaching pastures for their livestock. In the past, such protests have often ended in skirmishes between Yemenis and Saudi border patrol.
Saudi Arabia, the world's largest oil exporter, views its border with Yemen, often lawless and violent, as a major threat to its security.
Yemen is struggling to restore order after veteran leader Ali Abdullah Saleh stepped down following months of protests against his rule in 2011.
When Yemen's Shi'ite Muslim Houthi rebels seized some Saudi territory just across the border in 2009, Riyadh responded with a three-month military campaign including air raids on rebel positions. (Writing by Rania El Gamal; Editing by Sami Aboudi and Raissa Kasolowsky)