A homicide bomber struck a reconciliation meeting of Shiite and Sunni tribal leaders and senior provincial officials in Baqouba on Monday, killing at least 12 people, including the city's police chief, security officials said.

The bombing, which bore the hallmarks of Al Qaeda in Iraq, was a challenge to the U.S. strategy of turning members of both Islamic sects against extremists in a bid to duplicate the success in Anbar province to the west of the capital.

A witness to the attack said most of the people killed or wounded were in the mosque yard washing their hands or drinking tea after taking a break from the meeting for the iftar banquet, the daily meal to break the sunrise-to-sunset fast during the holy month of Ramadan.

Security officials, who spoke on condition of anonymity because they weren't authorized to release the information, also said 23 people were wounded, including several other senior provincial leaders.

Meanwhile, Iran closed major border crossings with northeastern Iraq to protest the U.S. detention of an Iranian official the military accused of weapons smuggling, a Kurdish official said.

Five border gates were closed starting Sunday night and continuing Monday morning, leaving travelers and cargo stranded, according to officials and witnesses.

The move threatens the economy of Iraq's northern region — one of the country's few success stories — and also appears aimed at driving a wedge between Iraq and the Americans at a time of friction over a deadly shooting in Baghdad involving the security firm Blackwater USA.

There were varying responses from Iranian officials to the border closures.

Iranian President Mahmoud Ahmadinejad, asked by The Associated Press, said the intent was to protect pilgrims.

"On an annual basis millions of Iranians visit Iraq and Iraq's holy sites for pilgrimage purposes," Ahmadinejad said in the interview in New York. "Recently as a result of some clashes and the explosion of some bombs a number of Iranian civilian casualties arose. So the government has asked Iranian citizens to avoid traveling for pilgrimage purposes until security is restored. The commercial goods and freight transactions continue and the travel across the border for those purposes continue."

However, the semiofficial Mehr news agency reported that five border points had been closed to protest the detention of the Iranian, who has been identified as Mahmudi Farhadi. He was arrested four days ago during a raid on a hotel in Sulaimaniyah, 160 miles northeast of Baghdad.

The closure will continue until Farhadi's unconditional release, the Mehr agency quoted Ismail Najjar, general governor of Iranian Kurdistan province, as saying.

Confusing matters even further, the public relations department at the Interior Ministry in Tehran said no decision had been made to shut the border.

U.S. officials said Farhadi was a member of the elite Quds force of the Iranian Revolutionary Guards that smuggles weapons into Iraq. But Iraqi and Iranian leaders said he was in the country on official business and with the full knowledge of the government.

Sulaimaniyah Gov. Dana Ahmed Majeed told the AP the move affected crossing points near the border towns of Panjwin, Haj Omran, Halabja and Khanaqin. A crossing at the town of Shena had remained open, but the mayor of the nearby town of Qalat Diza, Hussein Ahmed, said that gate was closed about 10 a.m.

Darseem Ahmed, an official at the gate near Haj Omran, 225 miles northeast of Baghdad, said up to 400 trucks use that crossing point daily.

A Kurdish merchant from Sulaimaniyah said he had three trucks loaded with construction materials stuck on the Iranian side of the border near Panjwin.

"They didn't allow them to cross, they closed the gate," Khalid Aman Sulaiman said, expressing concern the move would cause prices of imported products to spike. He said he would consider bringing the goods across illegal routes if the border points don't open within a week.

Jamal Abdullah, a spokesman for the autonomous Kurdish government, said the Iranian move "will have a bad effect on the economic situation of the Kurdish government and will hurt the civilians as well."

"We are paying the price of what the Americans have done by arresting the Iranian," he said.

Abdullah said the regional government had asked the central government to contact Iranian officials in Baghdad to stress that Kurdish authorities had no role in the detention.

"If this closure continues it will have an effect on the historical relations between the Kurdish government and the Iranian state," Abdullah added.

Iran has denied U.S. allegations that it is smuggling weapons to Shiite militias in Iraq.

"We don't need to do that. We are very much opposed to war and insecurity," Ahmadinejad reiterated in an interview with CBS' "60 Minutes" aired Sunday. "The insecurity in Iraq is detrimental to our interests."

But the U.S. insists it has evidence to the contrary. On Monday, U.S. troops killed one suspected militant and detained four others said to be involved in kidnapping operations run by Iranian-backed Shiite militias in Baghdad's Shiite district of Sadr City, the military said.

The latest detention of an Iranian official also has taxed relations between Iraq and the United States, already strained after the shooting deaths of 11 civilians at Nisoor Square in Baghdad on Sept. 16 — allegedly at the hands of Blackwater, one of three companies hired by the State Department to protect U.S. diplomats and other Western civilians.

Prime Minister Nouri 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 President Bush on the sidelines of the U.N. General Assembly.

Blackwater, of Moyock, N.C., denies its guards fired illegally and says they were defending themselves from armed insurgents.

Al-Maliki also condemned Farhadi's arrest, saying he understood the man had been invited to Iraq.

"The government of Iraq is an elected one and sovereign. When it gives a visa, it is responsible for the visa," al-Maliki told the AP in an interview Sunday in New York. "We consider the arrest ... of this individual who holds an Iraqi visa and a (valid) passport to be unacceptable."

Last week, President Jalal Talabani, a Kurd, demanded the Iranian's release and warned in a letter to America's top commander in Iraq, Gen. David Petraeus, and U.S. Ambassador Ryan Crocker that Iran had threatened to close its border with Iraq's Kurdish region over the case — a move that would cause considerable damage to trade in the prosperous Kurdish region.

Iranian Foreign Ministry spokesman Mohammad Ali Hosseini said Sunday that Farhadi was in charge of border transactions in western Iran and went to Iraq on an official invitation.

The U.S. military said the suspect was being questioned about "his knowledge of, and involvement in," the transportation of EFPs and other roadside bombs from Iran into Iraq and his possible role in the training of Iraqi insurgents in Iran.

On Monday, U.S. troops killed one suspected militant and detained four others said to be involved in kidnapping operations run by Iranian-backed Shiite militias in Baghdad's Shiite district of Sadr City, the military said.

In other violence, a homicide truck bomber struck an Iraqi checkpoint near the northern city of Tal Afar, killing three security forces and three civilians and wounding 16 other people, said Mayor Najim Abdullah.