An insurgent group linked to al-Qaeda in Iraq says it is holding two missing United States soldiers.
In an internet statement, the group said it had abducted the soldiers during an attack on a checkpoint near Yusufiya, south of Baghdad, on Friday.
Within minutes the group issued a second statement saying it had kidnapped four Russian diplomats and killed a fifth on 3 June.
The claims, on a site linked to militants, have not been confirmed.
They were posted by the Mujahideen Shura Council - a grouping of insurgents that includes al-Qaeda in Iraq.
The first message read: "Your brothers in the military wing of the Mujahideen Shura Council kidnapped the two American soldiers near Yusufiya."
One US soldier was killed during Friday's incident, but nothing had been heard of his two colleagues
They were named by the US military as Kristian Menchaca and Thomas Tucker, both from the 101st Airborne Division.
In the second message, the group said it had carried out an attack on a convoy carrying Russian diplomats in the Mansour area of Baghdad, where many embassies are based.
"God has enabled the lions of monotheism to arrest four Russian diplomats in Iraq and kill the fifth," the statement read.
The message urged Moscow to withdraw its troops from Chechnya within 48 hours or "face the consequences".
The claims came as US and Iraqi troops pushed further into the western Iraqi city of Ramadi.
Helicopter gunships provided air cover as troops and armoured vehicles pushed into the east of the city, one of the strongholds of the insurgency.