"Had the US foreign policy makers read history, they would not get involved in any war after Vietnam"
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A large amount of weapons were found during the operation, it said.
The clashes took place when security forces were carrying out a mission to restore essential services to the nearby town of Khalis.
Residents of Khalis, 80km north of Baghdad, told the Reuters news agency that fighters had shovelled earth into the irrigation canal some days ago, cutting off water to their farmlands.
The canal is in the Kobat area which, according to local residents, has a strong presence of al-Qaeda fighters.
US and Iraqi forces have been carrying out a series of operations in Diyala against the fighters. Pilgrims crowd Karbala
Meanwhile, pilgrims thronged the Iraqi city of Karbala to mark the 9th century birth of Muhammad al-Mahdi, the last of the 12 Shia imams revered as a saint.
Under tight security, they gathered at the city's two main shrines, forming long queues in the summer heat.
Police said they expect two million pilgrims to gather in Karbala on Tuesday.
An AFP reporter said that the atmosphere was calm and the mood was festive, in stark contrast to Monday evening when police fired on angry crowds, killing five pilgrims and wounding 30.
Witnesses said that the clashes began when pilgrims became angry at the long delays at checkpoints set up by security forces.
Call for calm
Sheikh Abdul-Hadi al-Mahamadawi, a leading cleric said in an address at the shrine of Imam Hussein: "We call on all parties to go back to their places and not to shoot."
"Everyone should comply with the orders of the leader Moqtada al-Sadr."
Shia pilgrims are often attacked on their way to Karbala while the city itself has been the site of suicide attacks and car bombs blamed on Sunni fighters.
In the worst incident, 44 people had died in a suicide attack targetting pilgrims in January 2006.
Police said that 15,000 security force members have been deployed across the city while medical officials said 53 ambulances and 24 medical teams are on standby.
A vehicle ban has been in place since Sunday.