By Frederik Richter and Lin Noueihed

MANAMA (Reuters) – Bahrain arrested at least six opposition leaders on Thursday, a day after its crackdown on protests by the Shi'ite Muslim majority drew rare U.S. criticism and raised fears of a regional conflict.
Bahraini forces used tanks and helicopters to drive protesters off the streets and clear a camp that had become a symbol of their demand for more democratic rights in the Sunni-ruled kingdom.

Three police and three protesters died in the crackdown.
The crackdown prompted sympathy protests from Shi'ites across the region and analysts said it might provoke a response from Iran, which supports Shi'ite groups in Iraq and Lebanon.

Pearl roundabout was a scene of devastation. Some tattered tents remained on the grass as diggers uprooted palm trees that surrounded the pearl statue where activists had been celebrating into the night only days before.
Troops were only allowing residents in and a long line of cars was backed up behind a checkpoint, waving through drivers heading to work in the financial district, where the protesters had tried to extend their sit-in early this week.
The military on Wednesday banned all protests and imposed a curfew from 4 p.m. to 4 a.m. across a large swathe of Manama.
Bank branches and coffee shops in the commercial district prepared to open. "It's back to normal, I can see traffic on King Faisal Highway. We drove all the way to work," said a bank employee.

OPPOSITION DETAINED

Among those detained overnight were Haq leader Hassan Mushaima and Wafa leader Abdel Wahhab Hussein, who had led calls for the overthrow of the royal family, the largest opposition party Wefaq said.
More moderate Wefaq had limited its demands to wide-ranging political and constitutional reform. Also arrested was Ibrahim Sharif, head of the secular leftist party Waad that signed up to the same demands as Wefaq.

"Two of the thugs climbed over the fence to get in our yard, one went over and pointed a gun in Ibrahim's face and the other went to our garage to let everyone else in," Farida Ismail, Sharif's wife, told Reuters by telephone. "They were going around, wrecking things in the house."

The interior ministry could not immediately be reached for comment and the charges against those arrested were not known.
The unrest has brought an influx of troops to Bahrain from Sunni-ruled neighbors Saudi Arabia, Qatar, Kuwait and the United Arab Emirates, which fear the uprising that began last month could play into the hands of non-Arab Shi'ite power Iran.

Washington's position appeared ambiguous.

Earlier this week, Washington said it understood why Bahrain's Sunni rulers had called in reinforcements. But on Wednesday, Secretary of State Hillary Clinton said force was not the answer.

"We find what's happening in Bahrain alarming. We think that there is no security answer to the aspirations and demands of the demonstrators," she told CBS. "They are on the wrong track."
A medical source said dozens of people were taken to Bahrain International Hospital on Wednesday, hit by rubber bullets or shotgun pellets or suffering teargas inhalation -- all weapons used by riot police. One was hit by a live bullet.

Protesters threw rocks and petrol bombs at police who were clearing the protest camp and killed three by running them over in cars at high speed, witnesses and medical sources said.
U.S. President Barack Obama called the kings of Saudi Arabia, a strategic ally of Washington in the Middle East, and of Bahrain, home to the U.S. Navy's Fifth Fleet and seen as a bulwark against Iranian influence, to urge "maximum" restraint.
But the violence appeared to dash hopes for political talks Washington hopes will take place.

SHI'ITE ANGER

Over 60 percent of Bahrainis are Shi'ites. Most say they want only the same treatment as Sunnis and a constitutional monarchy but calls by hardliners for the overthrow of the monarchy have alarmed Sunnis, who fear the unrest serves Iran.

Analysts say the intervention of Sunni-ruled Gulf Arab states in Bahrain might provoke a response from Tehran, which supports Shi'ite groups in Iraq and Lebanon.
"This was a major and a dangerous decision because this issue has been internationalized now. There are protests in Iraq, in Iran, in Lebanon," Wefaq MP Jasim Hussein said.

The crackdown galvanized Iraq's Shi'ite community, exacerbating sectarian tension that led to years of war in Iraq. Iraq's Shi'ite prime minister criticized the assault and Shi'ite cleric Moqtada al-Sadr called for protests.
In Lebanon, supporters of Shi'ite group Hezbollah came out in solidarity with their fellow Shia and Iran condemned Bahrain's response to the protests, recalling its ambassador for consultations. Iranian President Mahmoud Ahmadinejad said the crackdown was "unjustifiable."

Saudi Shi'ites held several demonstrations on Wednesday night, including one in their main regional center of Qatif where major Saudi oilfields are located, demanding the release of prisoners and voicing support for Shi'ites in Bahrain, an activist and witnesses said.

(Additional reporting by Erika Solomon in Dubai, Robin Pomeroy in Iran and Andrew Quinn in Washington; Editing by Diana Abdallah)