MANAMA, Bahrain -- Bahrain's capital was in lockdown mode Tuesday with stores shuttered and main highways blocked by police after a Saudi-led military force entered the Gulf kingdom in a sharp escalation of efforts to quell a pro-democracy uprising against the ruling monarch.
The dispatch of more than 1,000 troops from Gulf allies on Monday highlighted the regional worries about possible spillover from Bahrain, where members of a majority Shiite population have led a month of relentless protests against the Western-backed Sunni dynasty to try to break their monopoly on power.
Other Gulf leaders fear that concessions by Bahrain's rulers could embolden more protests against their own regimes, which have already confronted pro-reform cries in Oman, Kuwait and Saudi Arabia. There are also fears that gains by Bahrain's Shiite Muslims could offer a window for Shiite power Iran to expand its influence on the Arab side of the Gulf.
In Tehran, Iran's Foreign Ministry spokesman, Ramin Mehmanparast, denounced the presence of foreign troops in Bahrain as "unacceptable" and predicted it would complicate the kingdom's political crisis. Iran holds no deep political ties to Bahrain's Shiite groups, but some Iranian hard-liners in the past have hailed their efforts for greater rights.
Bahraini opposition groups also have strongly condemned the military move, calling it an occupation that pushes Bahrain dangerously close to a state of "undeclared war."
The United States -- which relies on Bahrain as a pillar of its military framework in the Gulf -- has urged Americans to avoid travel to the island nation due to "the potential for ongoing political and civil unrest." The State Department statement also advised Americans currently to consider leaving Bahrain, which hosts the U.S. Navy's 5th Fleet.
Many parts of Bahrain's capital, Manama, were nearly deserted. Most stores and malls were shut and schools were closed. Police barricades halted traffic on key roadways in apparent attempts to limit the movement of demonstrators.
Thousands of protesters held their ground in Manama's Pearl Square, the symbolic center of their revolt. But opposition leaders have not yet announced their next move.
Mansoor al-Jamri, editor of the main opposition newspaper, Al-Wasat, said pro-government mobs stormed the paper's printing facilities early Tuesday and smashed equipment with metal pipes, clubs and axes. The paper is now using presses from other papers to publish.
Shiites account for 70 percent of the population, but are widely excluded from high-level political or security posts. The protesters also demand the repeal of a government policy to offset the Shiite demographic advantage by giving citizenship and jobs to Sunnis from other Arab nations and South Asia.
The protests began last month with calls for the monarchy to give up most of its powers to the elected parliament. But as violence has deepened, many protesters now say they want to topple the entire royal family.
A statement Monday on the state-run Bahrain News Agency said troops from the six-nation Gulf Cooperation Council's Peninsula Shield Force have been deployed "in line with the principle of common destiny bonding." The bloc is made up of Saudi Arabia, Oman, Kuwait, Bahrain, Qatar and the United Arab Emirates.
Saudi Arabia and the UAE have announced roles in the Bahrain force, but the contributions from the other countries were not immediately clear.
The reason for the mission was "the common responsibility of the GCC countries in maintaining security and stability," the statement said.
The Peninsula Shield Force was created in the 1980s. Military units under a GCC command have been sent to Kuwait, including during the 1991 U.S.-led campaign to oust Saddam Hussein's force and in 2003 before the invasion of Iraq. The current action marks a significant shift to help a government quell internal unrest.
Jane Kinninmont, a senior research fellow and Bahrain expert at the London-based think tank Chatham House, said Monday's operation "changes the role of the GCC," which has always had collective defense pacts.
"The idea of gathering together to protect a government against its own people seems to be quite another thing," Kinninmont said.
In Washington on Monday, White House spokesman Jay Carney pointedly did not call on the Saudi-led force to withdraw.
"We are calling on the countries in the region to show restraint and pointing to the fact that the dialogue that can bring about political reform is essential for the stability of the countries in the region and their continued economic prosperity," Carney said.
Nasser Karimi contributed to this report from Tehran, Iran.