By Frederik Richter and Lin Noueihed
MANAMA (Reuters) - Bahrain's largest opposition group urged Saudi Arabia to withdraw its forces and called for a U.N. inquiry into a crackdown on mainly Shi'ite protesters that has angered Iran and raised tensions in the oil-exporting region.
Bahrain arrested seven opposition leaders on Thursday, a day after its forces moved in to end weeks of pro-democracy protests that have sucked in troops from its fellow Sunni-ruled neighbor and prompted the king to declare martial law.
"The military should withdraw from Bahrain, the military of Saudi Arabia, and this is a call to the Saudi king," Sheikh Ali Salman, head of Wefaq, told Al Jazeera television.
"We call for an investigation by the United Nations into what has happened from February 14 up to now. If protesters were in the wrong, then they should be held to account."
Three protesters died in the crackdown. Three policemen were also killed, hit by demonstrators in fast-moving cars.
The crackdown has drawn sympathy protests from Shi'ites across the Gulf Arab region, including the world's top oil exporter Saudi Arabia. Iran has complained to the United Nations.
Iran, which supports Shi'ite groups in Iraq and Lebanon, asked countries in the region to join it in urging Saudi Arabia to withdraw troops from the Gulf Arab island state.
"How could one accept a government to invite foreign military forces to suppress its own citizens?" Iran's Foreign Minister Ali Akbar Salehi said in a letter to U.N. Secretary General Ban Ki-moon, also addressed to the Arab League.
Bahrain said: "Iran's move does not serve security and stability in the Gulf region."
Over 60 percent of Bahrainis are Shi'ites. Most say they want 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.
Bahraini state TV called the detainees leaders of "civil strife" and said they had been communicating with foreign countries and inciting murder and destruction of properties.
It did not name the countries. Analysts say the intervention of troops from Saudi Arabia, which is concerned Bahraini protests could inspire its own Shi'ite Muslim minority, raises tension with Shi'ite power Iran.
Oil prices rose on Thursday as the Gulf tensions fueled fears of further supply disruption while investors weighed the impact on energy demand from quake-hit Japan. Capital flight from Bahrain is starting to pressure its currency and threaten its position as a Gulf financial center.
Most Western nations have urged their citizens to leave Bahrain.
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, Wefaq officials said.
More moderate Wefaq had limited its demands to 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."
In Geneva, U.N. High Commissioner for Human Rights Navi Pillay urged Bahrain to rein in its security forces, citing allegations that they had killed, beaten and carried out arbitrary arrests of protesters and attacked medical workers.
On Thursday, more than a dozen casualties who had been taken to Bahrain International Hospital during the crackdown were gone. Nurses said they had mostly been suffering from teargas inhalation and cuts and bruises. The wards were empty.
Tanks were still guarding the entrances to Salmaniya hospital on Thursday, after raiding the compound during the crackdown to clear tents that had been set up in the car park by opposition activists.
Pearl roundabout, focal point of weeks of protests, was a scene of devastation on Thursday. Some tattered tents remained as diggers uprooted palm trees that surrounded the statue where activists had been celebrating into the night only days before.
Troops were allowing only residents in and a long line of cars was backed up behind a checkpoint. They waved through drivers heading to work in the financial district, where the protesters had tried to extend their sit-in early this week.
The military, which is now in charge of Bahrain, banned all protests from Wednesday and imposed an open-ended curfew from 4 p.m. to 4 a.m. across a large swathe of Manama. The curfew was cut back by four hours in some areas on Thursday.
Kuwait said on Thursday its navy would had to Bahrain soon to protect its waters.
(Additional reporting by Amena Bakr and Erika Solomon in Dubai, Robin Pomeroy in Iran and Andrew Quinn in Washington; Writing by Lin Noueihed; Editing by Janet Lawrence)