WASHINGTON (Reuters) - At least four hostages held in Syria by Islamic State militants, including U.S. journalist James Foley, were waterboarded during their captivity, The Washington Post reported on Thursday, citing people familiar with the treatment of Western hostages.

The Islamic State captors appeared to model the technique on that of the CIA, which waterboarded three terrorism suspects captured after the Sept. 11, 2001, attacks on Washington and New York, the Post said. Foley was subsequently beheaded by his captors.

Waterboarding, a process characterized by President Barack Obama and many other U.S. politicians as torture, simulates drowning. Captives have water poured over their noses and mouths until they feel as if they are suffocating.

A source close to the family of a hostage held by Islamic State acknowledged to Reuters that hostages had been waterboarded, but gave no further details.

Three Americans and fewer than 10 other western hostages are still being held by the militant group, according to people familiar with the situation.

"They knew exactly how it was done," said a person with direct knowledge of what happened to the hostages, the Post reported. That person, who spoke on condition of anonymity, said Foley and the other captives were held in Raqqa, Syria.

The Post said a second person had confirmed that Foley was tortured, including by waterboarding.

“ISIL is a group that routinely crucifies and beheads people. It needs no inspiration for its brutality. To suggest that the U.S. is somehow responsible for ISIL tactics is ridiculous and feeds into their twisted propaganda,” said a U.S. official.

Foley was beheaded by Islamic State militants who posted a video of the killing on the Internet last week. The killer said his death was in retaliation for U.S. airstrikes on fighters in Iraq.

(Reporting by Jim Loney and Mark Hosenball; Editing by David Storey and Andrew Hay)