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BAGHDAD, Iraq (CNN) -- U.S. and Iraqi troops killed at least 68 al Qaeda militants in Iraq's Diyala province in the past four days, the U.S. military reported on Friday.

U.S. attack helicopters armed with missiles killed 17 "al Qaeda gunmen" Friday in and around a village southwest of Khalis, a volatile town in the province, the U.S. military said.

The military said the attack was part of Operation Arrowhead Ripper, the anti-insurgent offensive going on in and around Baquba, Diyala's provincial capital.

On Friday, attack helicopters spotted a group of armed men trying to avoid police and sneak into the village, the statement said.

Earlier, the U.S. military reported that through Thursday, troops had killed 51 al Qaeda militants in Baquba.

Twenty militants were detained, and seven weapons caches were discovered, the military said.

The military said troops destroyed 21 homemade bombs and nine booby-trapped structures, including an empty school complex, during the first three days of the operation, which began Tuesday.

Diyala province, north and east of Baghdad, is a sprawling district bordering Iran with a mixed ethnic and religious population.

Thousands of U.S. troops and Iraqi security forces are fighting in Diyala, where al Qaeda in Iraq militants have established a strong presence.

"We are shoulder-to-shoulder with Iraqi security forces in this fight," said Brig. Gen. Mick Bednarek, commander of Operation Arrowhead Ripper.

Arrowhead Ripper is one operation in a drive to take on insurgents in the towns and villages ringing Baghdad. Operation Marne Torch, southeast of Baghdad, and offensives in Anbar province, the Sunni-dominated region west of Baghdad, are also trying to rid the villages of militants.

Referring to Arrowhead Ripper, Bednarek said that the weeks ahead are crucial "in not only holding and retaining the ground that is cleared" but in winning the hearts of Diyala residents.

In other areas of Iraq, two more insurgents were killed and 37 others were detained Friday during coalition and Iraqi operations against al Qaeda in Iraq and Shiite militia groups, the U.S. military said.

Twenty-nine people were arrested in Mosul, Baghdad, Tarmiya, and Habbaniya. Eight were arrested in an operation south of Baghdad in Jabella.

Thursday night, violence in and near Baghdad left seven dead, according to the Iraqi Interior Ministry.

Three police officers were killed when a suicide truck bomb detonated outside an Iraqi National Police building southeast of Baghdad. Twenty people were wounded, including six police.

A roadside bomb near a U.S. convoy in southwestern Baghdad killed three civilians and wounded four others. Another roadside bombing, in western Baghdad, killed a police officer.

Meanwhile, 20 slain, unidentified bodies were found in Baghdad on Thursday, bringing this month's total to 430.

The U.S. military on Friday reported that a U.S. soldier was killed in combat Thursday in southwestern Baghdad, bringing the U.S. death toll for Wednesday and Thursday to 13.

The number of U.S. military deaths in the war now stands at 3,546, including seven civilian employees of the Defense Department. So far in June, 69 U.S. troops have been killed.

Army Lt. Gen. Ray Odierno, commander of the Multinational Corps-Iraq, said on Friday that three developments suggest progress for U.S.-led troops in Iraq.