Bahrain's king has declared a three month state of emergency in response to weeks of anti-government protests by majority Shi'ites against the Gulf state's Sunni rulers.
State television said Tuesday the king has ordered the commander of Bahrain's armed forces to take all necessary measures to stabilize the security situation.
The streets of Manama's financial district were deserted as the announcement was made, with many stores closed and police deployed on major highways.
About 1,000 Saudi soldiers and 500 police from the United Arab Emirates crossed into Bahrain Monday via the causeway that connects it with mostly-Sunni Saudi Arabia. The two neighboring states say they were answering a call for help from Bahrain's monarchy to protect government buildings from opposition protesters.
Predominantly Shi'ite Iran said Tuesday the military intervention in Bahrain is “unacceptable.” Bahrain's Shi'ite opposition also has denounced the deployment of Gulf troops as an “occupation.”
Bahrain invoked the collective security agreement of the six-nation Gulf Cooperation Council. But it remains unclear whether other members of the bloc — Oman, Kuwait and Qatar — will also contribute forces.
The U.S. State Department Tuesday warned its citizens against travel to the Gulf country and advised Americans in Bahrain to consider leaving. It said U.S. citizens should avoid all demonstrations because they could escalate into violence.
In Washington, a White House spokesman called on countries of the Gulf region to show restraint but said the United States does not consider the arrival of foreign forces in Bahrain an invasion. He did not call for the withdrawal of the Saudi and UAE forces.
Oil-rich Bahrain is home to the U.S. Navy's Fifth Fleet, which provides support to U.S. troops in Iraq and Afghanistan.
U.S. Defense Secretary Robert Gates was in Bahrain on Saturday and urged the government to institute reforms. He also expressed concern that the on-going protests could provide an opening for Shi'ite Iran's government to escalate sectarian tensions in the region.
Bahrain's ruling al-Khalifa family has offered to hold a dialogue with opposition groups on democratic reforms, but protesters want the government to meet their demands first. Some opposition groups want the creation of a constitutional monarchy in which the parliament has more power, while others seek the ouster of the ruling family.