"One marine ... was killed in action on 20 September and another died of wounds received in action while conducting security and stability operations in al-Anbar province," it said in a statement.
Elsewhere four US soldiers were injured when a booby-trapped car exploded next to a military convoy along the highway southwest of Baghdad.
The US army said two military vehicles were destroyed in the explosion, while three Iraqis were killed and 16 others were injured, including four from the Iraqi National Guard.
One Iraqi died and three others were injured in a roadside explosion in the city of Baquba.
The attack was one of many throughout Iraq on Tuesday.
The attack targeted an Iraqi police patrol in the city, 60km northeast of Baghdad.
The explosion took place after the patrol passed near an equestrian club. Casualties were transferred to Baquba's general hospital.
The city has been the scene of growing unrest. In August a pipeline was blown up when the country's oil infrastructure was hit by a string of attacks.
Meanwhile, US marines arrested two close aides of Shia leader Muqtada al-Sadr in a raid on Monday at his office in the central Iraqi city of Najaf, officials in al-Sadr's office and witnesses said.
Close aides of Muqtada al-Sadr
were arrested in Najaf
"A group of US marines raided the office of Sayyid al-Sadr at 2200 GMT (2am) and arrested Shaikh and Sayyid Husam al-Musawi and a number of other workers in the office," said Abu Sadiq al-Adhari.
Al-Shaibani is said to be one of al-Sadr's most outspoken aides in Najaf.
Shaikh Asad al-Basri, head of al-Sadr's office in Basra, told Aljazeera: "Ahmad al-Shaibani and one of the office's guards have been arrested, though there are only few office members there.
"Iraqi police have previously entered the office, in coordination with Muqtada al-Sadr, and confiscated some arms," he said.
He said the action was part of an attempt to escalate the situation.
"We call on all related sides to prevent war, bloodshed and destruction in Iraq and Basra, particularly if violating the truce has continued," he said.
Elsewhere in Iraq:
A car bomb hit a US military convoy near a bridge over the highway leading to Baghdad's airport. One Iraqi died and several people were wounded, including four US soldiers.
US forces and Iraqi police detonated a booby-trapped car parked behind al-Mulla Hwaish mosque in Rabia street in western Baghdad. The vehicle was parked outside an Iraqi National Guard recruiting centre. Its driver managed to escape after being pursued by police, witnesses said.
In Mosul, a blast damaged four vehicles and wounded four passengers.
In Samarra's southern Balad area, a US patrol was hit by an explosive device. No casualties were reported.
In Tarmiya, northern Baghdad, a US military convoy was attacked.
A US military Humvee was attacked near Abu Ghraib.
A car bomb hit a US military convoy near a bridge over the highway leading to Baghdad's airport, injuring several people.