BAGHDAD: Gunmen in four cars opened fire Wednesday on a convoy of buses carrying Iranian pilgrims on their way to the holy Shiite city of Najaf, killing five of them, Iraqi police said.

Some 35 others were also wounded in the attack, which took place near the village of Kebasi about 100 miles (170 kilometers) north of the capital.

Hundreds of thousands of pilgrims — many of them from neighboring Iran — travel to Iraq every year to visit Shiite holy sites including the cities of Najaf and Karbala, and the Kazimiyah shrine in Baghdad. Many of the Iranian pilgrims travel over land through Diyala province which borders Iran and then on to Baghdad as well as Najaf and Karbala south of the capital.

The convoy was being escorted by police when it came under attack, the official said. Iraqi police exchanged gunfire with the gunmen, who fled after the attack, he said.

The police official spoke on condition of anonymity because he was not authorized to speak to the media.

One woman was among the dead, the official said.

Under Saddam Hussein's Sunni-led regime, Shiite pilgrims, especially from Iran, were discouraged from visiting the holy cities. Since his ouster, pilgrims have traveled to Iraq by the millions for religious occasions and have become a major target of Sunni insurgents.

The U.S. military also said that two attackers and a bystander were killed Tuesday when an American convoy was attacked in the Abu Ghraib area west of the capital.

Lt. Col. Philip Smith, the U.S. military spokesman said the attack involved grenades and small arms fire. Four other civilians were also wounded.

"The grenades the enemy were attempting to throw exploded," Smith said in an e-mail message. "Additional enemy forces fired small arms fire at the convoy from a nearby alley."

An Iraqi police official gave a conflicting account, however, saying four civilians — a boy and three bus drivers — were killed when U.S. forces opened fire on the attackers near a bus station. He requested anonymity because he was not allowed to speak to the media.

Resident Jabbar Jassim told The Associated Press that he believes it was American gunfire that killed his 11-year-old son, Hisham, while they were waiting in line at the bus station.

Under an Iraqi-U.S. security pact, American combat troops withdrew from the country's cities last month.

Smith said the convoy was on its way to an Iraqi police station to participate in a joint exercise.