U.S. opens criminal probe into journalist Foley's death - Holder

U.S. journalists James Foley (2nd R) and Clare Gillis (R) arrive, after being released by the Libyan government, at Rixos hotel in Tripoli, in this photograph taken May 18, 2011. REUTERS/Louafi Larbi

WASHINGTON (Reuters) - The U.S. Justice Department is conducting a criminal investigation into the death of American journalist James Foley, Attorney General Eric Holder said on Thursday.

Foley was beheaded by the Islamist militant group Islamic State, an act shown in a video released on Tuesday in which the group called for the United States to end its airstrikes in Iraq. Obama responded that the United States would be relentless in fighting the organisation despite the killing.