U.S.-led forces detained six Iranians Thursday at a government office flying an Iranian flag, Iraqi officials and witnesses said, raising tensions as U.S. President George W. Bush moves to isolate Iran and Syria as part of his new strategy to quell violence in Iraq.

The arrests in the northern city of Irbil — the second targeting Iranians in less than a month — drew condemnation from the regional Kurdish government and concern from national officials as they try to balance Iraq's close ties with Iran and the rivalry between Tehran and Washington.

Top U.S. officials reiterated longstanding accusations that Iran is helping to fuel the violence in Iraq with weapons and money.

"I think it's instructive that in the last couple of weeks two of those raids that we conducted to go after these folks that are providing these kinds of weapons — two of those raids had policed up Iranians," Gen. Peter Pace, chairman of the Joint Chiefs of Staff, said in Washington. "So it is clear that the Iranians are complicit in providing weapons."

In Tehran, Iran's Foreign Ministry summoned the Iraqi and Swiss ambassadors and "demanded an explanation" about the incident. Switzerland represents American interests in Iran, where there is no U.S. Embassy.

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The multinational forces entered the building overnight, detaining the Iranians and confiscating computers and documents, two senior local Kurdish officials said, speaking on condition of anonymity because of the sensitivity of the information. Irbil is in the Kurdish-controlled north, 220 miles from Baghdad.

A resident living near the mission said the foreign forces used percussion grenades and brought down an Iranian flag from the roof of the two-story yellow building. As the operation went on, two helicopters flew overhead, the resident said, speaking on condition that his name not be used because he feared retribution.

In the early afternoon, a number of Kurdish guerrillas could be seen around the building preventing people from getting close to the house and not allowing cameramen and photographers to take pictures.

U.S. Ambassador Zalmay Khalilzad said the detained Iranians were being questioned, but he did not give more details.

The arrests came as tensions are high between Iran and the United States. The Bush administration has accused Iran of seeking to develop nuclear weapons and of helping fuel violence in Iraq. Iranian President Mahmoud Ahmadinejad, meanwhile, is trying to expand Tehran's role in Iraq as a counter to U.S. influence in the Gulf region.

Iraqi government spokesman Ali al-Dabbagh said the government was seeking clarification from the Americans and the Iranians about the detainees, but he chided both sides, along with U.S. rival Syria, for using Iraq to fight their political battles.

"Sometimes we pay the price for the tension in relations between Iran and the United States and Syria, therefore it is in our interest ... that these relations improve, but not at the expense of Iraq," he said.

Bush's new strategy, however, ignored key recommendations of the Iraq Study Group, which in December called for a new diplomatic offensive and an outreach to Syria and Iran. Instead, he accused both countries of aiding terrorists and insurgents in Iraq.

"We will disrupt the attacks on our forces," Bush said in a speech outlining his new war strategy. "We will interrupt the flow of support from Iran and Syria."

Politicians and ordinary Iraqis, meanwhile, expressed skepticism Thursday that Bush's plan to send 21,500 more troops to Iraq will quell the violence in their country on a day in which police reported at least 48 people were killed or found dead from bombings and shootings, including a 10-year-old child struck in a mortar attack in Mosul.

An aide to Prime Minister Nouri al-Maliki welcomed the new strategy but stressed that the government must take the lead in the military action. The plan also envisions 10,000 to 12,000 Iraqi troops to secure Baghdad neighborhoods, and al-Maliki has announced plans for a new Iraqi security operation, although similar efforts have been unsuccessful.

"The failure in Iraq will not only affect this country only but the rest of the region and the world, including the United States," al-Maliki aide Sadiq al-Rikabi said, adding "the Iraqi government also is committed to succeed."

Sunni lawmaker Hussein al-Falluji rejected the plan to send more U.S. troops and called instead for a timetable for them to withdraw. Adnan al-Dulaimi, leader of parliament's largest Sunni Arab bloc, urged the Americans and the Iraqi government to make sure the militias are disbanded and to ensure the Shiite-dominated security forces are neutral, as they have been accused of targeting Sunni insurgents while allowing militias to run amok.

"These security services should not be for one sect," he told Iraqi state television. "We see also ... the presence of the American troops on Iraqi streets is considered a kind of reassurance to Iraqis because the American troops will be neutral."

But some offered weary acceptance of any effort to stop the carnage after several failed past attempts.

"The security situation in Iraq is very bad, we are facing death at any moment daily," 35-year-old technician Awad Mukhtar said. "I see the new Bush strategy as the last chance for Iraqis to save their lives ... we have no other choice, only to wait and see the results."

Iraqi and Iranian officials initially said the office targeted in the raid in Irbil was a diplomatic mission, but Iran's Foreign Ministry spokesman Mohammad Ali Hosseini later changed the description to an "office of relations."

"The office was waiting for permission from the Iraqi authorities to operate as a consulate," Hosseini said, according to Iranian state television. He did not describe the Iranians who worked there as diplomats. "The office was established in coordination with, and with the agreement of, the Iraqi authorities. It was performing some consular affairs."

At the Pentagon, a senior U.S. military official said the building was not a consulate and did not have any diplomatic status. The six Iranians were taken in a "cordon-and-knock" operation, said the official who spoke on condition of anonymity because he was not authorized to release the information.

The regional Kurdish government condemned the arrest of the Iranians and called for their immediate release. It added that the government "was not aware in advance of the raid."

Many Kurds, including Iraqi President Jalal Talabani, have close ties to Iran before Saddam Hussein was overthrown by the U.S.-led invasion in 2003.

Late last month, U.S. troops elsewhere in Iraq detained at least two Iranians and released two others who had diplomatic immunity. Two of those detained were visiting as guests of Talabani, his spokesman said.

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