WASHINGTON: The United States voiced concern over unrest in US Gulf ally Bahrain and urged restraint as top officials Thursday spoke to their Bahraini counterparts.

The telephone calls were the latest signs of growing administration anxiety over instability in the home of the US Fifth Fleet and neighbor of another leading US ally, oil-rich Saudi Arabia.

Speaking to Bahrain's foreign minister Sheikh Khaled bin Ahmad al-Khalifa, Secretary of State Hillary Clinton "expressed deep concern about recent events and urged restraint moving forward," a State Department official said.

Bahrain's military deployed armored vehicles in the center of the capital Manama and vowed to restore order Thursday after a violent police raid on anti-regime protesters left four people dead and scores wounded.

Clinton and Sheikh Khaled also "discussed political and economic reform efforts to respond to the citizens of Bahrain," the US official added.

Inspired by protests that toppled presidents in Tunisia and Egypt, thousands of people have taken to Bahrain's streets to call for a change of regime and a "real constitutional monarchy" in the Sunni-led but Shiite-majority country.

Defense Secretary Robert Gates "discussed the current security situation" in his call the Deputy Supreme Commander of the Bahraini Defense Force," press secretary Geoff Morrell said in a statement, offering no other detail.

John Kerry, chairman of the Senate Foreign Relations Committee and a Democratic lawmaker who is close to the administration, meanwhile condemned the violence in Bahrain.

"Using tear gas, batons, and rubber bullets on peaceful protesters is the worst kind of response to a nonviolent demonstration," Kerry said in a statement.

"I urge the government of Bahrain to put an end to the violence and allow the Bahrainis to voice their call for greater political freedom," he said.

"Historic protests are taking place across the Arab world and it is vital for every government to respond peacefully and listen to their own people," Kerry added.

On Tuesday, Obama warned all Arab and Middle Eastern rulers that they should get ahead of the wave of protest by moving towards democratic reforms after decades of autocratic rule.

The White House said Wednesday it was watching the unrest in Bahrain "very closely" and called on the pro-Western kingdom to allow peaceful anti-government protests.

Bahrain serves as headquarters for a pillar of American military power, the US Navy's Fifth Fleet, which commands a rotating flotilla of vessels charged with safeguarding oil shipping lanes in the Gulf and countering Iran.

The archipelago of Bahrain is also an important banking and oil refining center that is linked via causeway to Saudi Arabia, which has a sizeable minority Shiite population that has been restive in the past.

Anthony Cordesman, a former intelligence analyst for the Department of Defense, said Bahrain's Shiites are focused on lack of jobs and their political marginalization rather than on the US presence in Bahrain.

Cordesman, analyst with the Center for Strategic and International Studies who still offers his expertise to the US government, said that "for a long time, the US has tried to persuade the regime to be more open and to address the grievances of Shiites," who rioted in the 1990s.

He said the current unrest is not so much "a direct threat to the United States as the fact that any instability in an important country is a problem."

But he said the naval base in Bahrain -- which coordinates naval exercises and training for Gulf Arab navies, is "very important" in light of the "steady buildup" in the last decade by the naval branch of Iran's Revolutionary Guards.