DUBAI: Saudi Arabia vowed to use ''an iron fist'' after 11 members of the security forces were injured during unrest in a Shiite Muslim town in the east, the official Saudi press agency said.

The government accused an unnamed foreign country of seeking to undermine the stability of the kingdom as a result of the violence in Awwamiya, in which the assailants, some on motorcycles, used machine guns and Molotov cocktails, the Riyadh news service reported on Tuesday. A man and two women were also hurt, the news service said.

Saudi Arabia, the world's largest oil supplier, escaped the mass protests that toppled the leaders of Egypt and Tunisia this year and spread to Yemen and Bahrain. There were some rallies earlier in the year in mostly Shiite eastern Saudi Arabia, including Awwamiya and al-Qatif village.

Predominantly Sunni Muslim, Saudi Arabia has accused Shiite-led Iran of interfering in the affairs of Arab countries in the Persian Gulf, home to three-fifths of the world's oil reserves. Saudi Arabia and other Gulf countries sent troops to Bahrain in March to quell the mainly Shiite unrest.

''Given that this happened in the predominantly Shiite area of Saudi Arabia, in its east, this could be a sign of greater trouble ahead,'' Paul Sullivan, a political scientist in Middle East security at Washington's Georgetown University, said. ''Shiite-Sunni tensions are building in the region and Iran is one of the major culprits behind it.''

King Abdullah announced $US130 billion ($136 billion) in spending in February and March in a bid to ensure the Arab Spring did not spread to Saudi Arabia, where its Shiite minority is concentrated in its eastern oil-producing hub.

The US State Department noted in a report on Saudi Arabia in 2009 that Shiites in the kingdom face ''significant political, economic, legal, social and religious discrimination condoned by the government''.

Saudi Arabia enforces restrictions interpreted from the Wahhabi version of Sunni Islam. In addition to restrictions on women, practices of other branches of Islam are limited.

Bloomberg