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By Amena Bakr
DUBAI, July 12 (Reuters) - Saudi Arabia has deployed more troops in its oil-rich Eastern Province and cancelled some military leave amid worries about new unrest among Shi'ite Muslims in the kingdom and regional tensions, Saudi government sources and diplomats said on Thursday.
A Saudi government source said that top commanders, in a directive issued on June 26, ordered extra security forces to be stationed in the kingdom's crude-producing east where the majority of the Saudi Shi'ite population live.
The source said Saudi troops were put on alert and summer leave was cancelled for some officers but "those already on holiday are not being called back." Western diplomats confirmed that holidays were suspended since the end of June.
Speculation about an Israeli attack on Iran, locked in a standoff with Western powers over its disputed nuclear programme, is again on the rise. The West believes Iran is trying to develop nuclear weapons, a charge Tehran denies.
Israel has hinted it may attack Iran if diplomacy fails to secure a halt to nuclear enrichment. The United States has also mooted military action as a last-resort option but has frequently nudged the Israelis to give time for intensified economic sanctions to work against Iran.
Iran has threatened to destroy U.S. military bases across the Middle East and target Israel within minutes of being attacked, according to Iranian media reports last week.
Saudi Arabia, a key U.S. ally in the region, fears that any Israeli attack on Iran could involve retaliatory strikes on its territory, or it might ignite protests among its restless Shi'ite community.
The shooting down of a Turkish jet plane by Iran's regional ally, Syria, has ratcheted up tensions and increased worries of an imminent conflict, the sources said.
"It's been the norm for a long time that the National Guard is ready for backup for any security threat," the source added.
The source said that up to 1,200 additional National Guard members - an elite Bedouin corps led by King Abdullah's son Prince Miteb that handles domestic security - had been sent to the Eastern Province.
"The deployment has been taking place as a show of force ... a deterrent policy," he said, adding that the total count of National Guard forces in the region was now more than 3,000.
Officials from the Interior and Foreign ministries referred calls to the Defence Ministry and no spokesman was available to comment.
Columnist David Ignatius, writing in the Washington Post on Thursday, said that Saudi Arabia had alerted some of its military and security officials to cancel their summer leaves.
"Saudi and U.S. sources say this limited mobilization reflects worries about possible military conflict with Iran, the war of succession in Syria, and Sunni-Shi'ite tensions in neighboring Bahrain," he wrote.
Sunni Muslim Saudi Arabia has already accused Shi'ite Iran of fomenting unrest in the Qatif region of the Eastern Province, home to many of the kingdom's Shi'ite minority, and in neighboring Bahrain, charges Tehran denies.
Saudi Arabia and Iran are regional rivals and have backed opposing sides in the violence convulsing Syria.
Western diplomats confirmed that more Saudi security forces have been deployed to the Eastern Province, saying it was related to Iran but gave no further details.
Two Saudi Shi'ites died during protests with police in the Qatif region this month after a Shi'ite cleric was arrested.
Saudi Arabia may be further worried about Tehran's reaction after a European Union oil embargo, widely expected to hurt Iran's vital energy exports, went into effect on July 1 over its disputed nuclear programme.
Iran has threatened to shut down the Strait of Hormuz, a strategic waterway at the mouth of the Gulf where about a third of sea-borne oil exports pass, if it came under attack over its disputed nuclear programme.
A member of Iran's National Security and Foreign Policy Committee said on July 2 it had drafted a bill calling for Tehran to try to stop oil tankers from shipping crude through the Strait to countries that support sanctions against it.
Saudi Arabia has already taken some precautionary steps against the possibility of Iran shutting down the Strait, including the reopening of an old pipeline built by Iraq to bypass the channel and export more crude via the Red Sea terminals.
The United States has also sent four minesweepers to the Gulf to bolster the U.S. Fifth Fleet after an Iranian military chief refreshed threats to block Hormuz.
Analysts played down the likelihood of Iran being able to stir up protests in eastern Saudi Arabia.
"I suppose you do have to take some consideration of the fact that there might be unrest in the Shi'ite provinces should there be any tension (between Turkey and Syria)," Stephens said.
But the Iranians did not have that much sway in the Eastern Province. "It's not like they can just call someone up and tell them to make trouble," he added. (Reporting by Amena Bakr; Additional reporting by Isabel Coles Editing by Sami Aboudi and Samia Nakhoul)