SULAIMANIYAH, Iraq, 25 September 2007 — Iran closed its border with northern Iraq yesterday in protest at the detention of an Iranian by US troops, a day after it confirmed shelling Iraqi rear bases of separatist Kurdish rebels.

“All five entry points on the border between Iran and the (Iraqi) Kurdish region have been closed by the Iranian authorities from today,” said Jamal Abdallah, spokesman for the autonomous Kurdish regional government.

Iran confirmed it had shut the border following the detention of Mahmudi Farhadi by US forces on Thursday. The US military charges that Farhadi is an officer in the covert operations arm of Iran’s elite Revolutionary Guards, accused by American commanders of helping Shiite militias involved in Iraq’s bloody sectarian conflict.

“We have closed the border and we hope the Iraqi authorities will act as quickly as possible to release our colleague,” the governor of Iran’s northwestern Kordestan province, Esmaeel Najar, told AFP. “We had said that if he (Farhadi) was not freed rapidly, we would reconsider our commercial ties” with the Iraqi Kurdish region, Najar added.

Asked when the border would reopen, he replied: “We hope that the Iraqi authorities will act as swiftly as possible to free our colleague.” Iran has made clear that it regards Iraq’s sovereignty as being at stake in Farhadi’s continued custody after both the regional and national authorities said he had been visiting with their consent.

The escalation of the dispute comes with Iraqi sovereignty also at issue in the future of US private security firm Blackwater after a Baghdad shootout involving its staff in which 10 civilians died last week.

Iraqi President Jalal Talabani, himself a Kurd, had warned senior US officials on Saturday that Iran was poised to close the border over the Farhadi affair. In an indignant letter to Gen. David Petraeus, the commander of US forces in Iraq, and US ambassador Ryan Crocker, Talabani said the arrest of an Iranian official at the invitation of the Kurdish authorities was “a humiliation for the regional administration.”

Meanwhile, the Iraqi government said it will await the outcome of a probe into the deadly Baghdad shootout on Sept. 16 involving Blackwater before taking any action against the company. “The future of Blackwater is linked to the joint US and Iraqi investigation. But we will put the lives and dignity of Iraqis above all considerations,” government spokesman Ali Al-Dabbagh said.

Blackwater, the biggest private security firm operating in Iraq, said its guards fired in response to a car bomb, but a senior police officer said the shooting was unprovoked. Iraqi officials, meanwhile, said insurgents killed at least 10 people across Iraq yesterday, including six in a suicide truck bomb attack in the northern town of Tal Afar.

Prime Minister Nuri Al-Maliki has said the Blackwater incident was among several “serious challenges to the sovereignty of Iraq” by the company, adding he would take the case up in discussions with US President George W. Bush in New York, on the sidelines of the UN General Assembly.