Iraqi police and army troops fanned out around Karbala on Friday to safeguard the Shiite holy city, as a mortar attack killed three pilgrims heading there for a religious festival.

At least 22 others were wounded — four critically — when three mortar rounds struck pilgrims in Musayyib, about 40 miles south of Baghdad.

Officials said they expected as many as 3 million pilgrims at the religious festival Saturday in Karbala, 50 miles south of Baghdad.

"Our forces have tightened their control on the ground and our only concern now is rockets launched from a far distance," said Iraqi army Maj. Gen. Samir Abdullah.

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Millions attend the festival observing the birthday of Imam al-Mahdi al-Muntadhar, a 9th-century religious leader. Many walk to Karbala from across Iraq, and several attacks already have occurred on processions heading to the city.

On Monday, Iraqi soldiers clashed with gunmen near Karbala during an operation to secure the area, leaving 14 militants and one Iraqi soldier dead, the prime minister's office said. Last week, 13 Pakistani and Indian Shiite pilgrims and their Iraqi driver were ambushed and killed en route to the city.

Since the 2003 U.S.-led invasion of Iraq, Karbala has seen a number of attacks — mostly involving suicide bombers — that have killed hundreds of people. The attacks are considered to have been the work of Sunni Arab extremist groups, including Al Qaeda in Iraq, that consider Shiites to be heretics and American collaborators.

Iraqi officials said police and army troops had deployed around Karbala ahead of Saturday's festival to prevent the infiltration of suicide bombers and terrorists. Cars have been banned since Wednesday.

"We arrested two terrorists who were trying to enter Karbala and they confessed that there were other elements who wanted to enter and target Shiites," Karbala governor Aqil al-Khazali said.

One of the army units that will defend Karbala, al-Farhoud's 8th Division, was the first to come under full Iraqi control during a ceremony Thursday. U.S.-led forces turned over control of Iraq's military command to the Shiite-led government, a step considered key toward the eventual withdrawal of foreign troops.

Meanwhile, Prime Minister Nouri al-Maliki's government defended its decision to shut down the Baghdad operations of Al-Arabiya, a Dubai-based satellite TV channel, for one month.

Spokesman Ali al-Dabagh said some of Al-Arabiya's reporting staff promoted sectarian violence and that some of its reports supported "terrorism." He did not name any reporters.

"Some hostile reports try to describe the situation in Iraq as if it is already fallen into a civil war, this is a problem and this is a support for terrorism," he told Iraqi state television.

The other pan-Arab satellite network, Al-Jazeera, had its office in the capital closed two years ago.

Also Friday, coalition authorities announced the deaths of two soldiers — an American and a Briton.

The U.S. soldier was killed Friday by a roadside bomb explosion south of Baghdad. The British soldier died Thursday of wounds suffered earlier in the week when his patrol came under fire in Qurnah, about 35 miles north of Basra.

In other violence, a roadside bomb targeting a police patrol in Baghdad killed two people and wounded six, police said. A roadside bomb also struck an Iraqi army convoy near Karmah, 50 miles west of Baghdad, killing four Iraqi soldiers.

Four bodies, all shot in the head and bound to each other with a chain, were found on a river bank 40 miles southwest of the capital, the morgue in the city of Kut said.

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