The claim was made in a new video recording released today by the Islamic State In Iraq.
An unidentified voice made the claim on the video, which was made available to Western news agencies by the Washington-based Search for International Terrorist Entities (SITE) Institute.
The video does not offer any proof that the soldiers were killed and does not show them.
The three soldiers have been missing since mid-May. The body of one soldier was later found, but the other two are still missing.
In other news, Iraqi police say at least 12 people, including seven insurgents, were killed across Iraq today.
Also, Pope Benedict XVI said today he is "deeply saddened" by the murder of a Catholic Chaldean priest and three of his assistants in northern Iraq on June 3.
In a telegram, Paul Faraj Rahho, the pope's secretary of state, said the pope wished to convey "heartfelt condolences" to the victims' families over the "senseless killings."
(AFP, AP, Reuters, CNN)
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