BAGHDAD, Iraq (CNN) -- Bombings, clashes and a shooting in Iraq Tuesday left at least 48 people dead, and another 20 bodies were found in a mass grave, police officials told CNN.
An Iraqi girl walks Tuesday past a tank north of Baghdad that was destroyed in the early days of the war.
Police and a local citizens group found five children, six women and nine men in the grave, just northeast of Samarra.
Authorities said the victims were kidnapped at least two months ago by al Qaeda in Iraq. The victims were blindfolded, bullet-riddled and bound, with some showing signs of torture, officials said.
Families working with the Iraqi government or security forces have been targeted by militants.
A weapons cache containing mortar rounds, rocket-propelled grenades, explosives, suicide vests and car bombs was found near the grave.
Those events came a day after eight U.S. soldiers died in two separate bombings in Baghdad and in Diyala province, and a leading sheikh in a Diyala province town was killed by a female suicide attacker, officials said. 
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Tuesday, at least 10 people were killed and 28 wounded when clashes erupted between Iraqi security forces and Shiite militiamen in the central Iraq city of Kut, according to an official with the nation's Interior Ministry.
The clashes happened while Iraqi police and army were raiding three neighborhoods in the city searching for wanted militants, the official said. The neighborhoods are known strongholds of militants loyal to radical Shiite cleric Muqtada al-Sadr. A vehicle curfew was imposed in the city after the skirmishes, as sporadic gunfire could still be heard, the official said.
U.S. Special Forces, responding to a request for support from Iraqi security forces, destroyed a vehicle carrying weapons and explosives and also gunned down several enemy fighters, the U.S. military said.
Kut is about 160 km (about 100 miles) southeast of Baghdad in Wasit province.
Seven Iraqi citizens were killed Tuesday and 11 injured near Balad in a car bombing at the headquarters of the awakening group Sons of Iraq, the U.S. military said.
"A Sons of Iraq member fired his weapon at the driver of the explosive-laden pickup truck after realizing his intent, but the driver was still able to detonate the bomb," a military statement said.
Also Tuesday, nine people, including four police officers, were killed when clashes broke out between insurgents and Iraqi police in Mosul, about 420 km (about 260 miles) north of Baghdad, according to an official with Mosul police. Four gunmen and a civilian also were killed, according to police. The Interior Ministry confirmed the information.
In other Iraq violence:
• An American soldier died and two others were wounded after a roadside bomb went off near a south-central Iraqi town, the U.S.-led military command said Wednesday. The soldier, whose name has been withheld until family members are notified, was on patrol near Diwaniya on Tuesday. This latest casualty followed the deaths of eight U.S. troops in two bombings Monday.
• Sixteen people died and 22 were wounded Tuesday when a roadside bomb in southern Iraq struck a passenger bus.
• Five people were killed and 14 were wounded when a suicide bomber slammed into a police-security volunteer checkpoint in Dhuluiya in northern Iraq's Salaheddin province. The bomber, driving a small pickup truck, struck a checkpoint manned by police and members of the local Awakening Council, the U.S.-backed security volunteers.
• A gunman in northeastern Baghdad shot at a minibus carrying employees from Iraq's Electricity Ministry, killing one person and wounding eight.
• Other mass graves have been found recently, including one discovered Saturday with up to 100 bodies just north of Baquba in Diyala province.
• Monday, U.S. troops in the Mosul area killed a senior al Qaeda in Iraq leader thought to be responsible for car bombings and made four arrests in a pair of raids over the last 24 hours, the U.S. military said.
"Coalition forces confirmed the location of the wanted AQI [al Qaeda in Iraq] leader and a supporting helicopter was called to engage, killing him and another terrorist, and destroying the vehicle they were operating in," the military said.
• Saudi fighters were targeted in two operations in western and southeastern Mosul Tuesday, the military said. Four people were seized.
• In other operations, three insurgents were killed north of Dawr Monday. Arrests were made on Tuesday in Baiji, west of Samarra, near Tikrit, and in Abu Ghraib. E-mail to a friend 
CNN's Mohammed Tawfeeq and Joe Sterling contributed to this report.
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