The Islamic State of Iraq and the Levant (ISIL) has released a video showing British journalist John Cantlie, who is being held hostage by the fighters, appearing to criticise US-led attacks on the group, the SITE monitoring service has said.

The five-minute video was posted online on Tuesday, just hours after a wave of strikes, including attacks by warplanes and cruise missiles, were launched by the US and partners of a coalition against ISIL targets in Syria.

Reading from a script, Cantlie, who was taken captive by the fighters in 2012 while covering the conflict in Syria, warned that Washington and its allies were embarking on what he described as a "third Gulf War", SITE reported.

The footage, which appeared to be made as a form of propaganda by ISIL, showed Cantile saying that "not since Vietnam have we witnessed such a potential mess in the making".

Cantlie says that the strikes against the "most powerful jihadist movement seen in history" could not harm it and quotes statements by US officials warning Washington against battling ISIL.

"Current estimates of 15,000 troops needed to fight ISIL are laughably low. The State has more mujahidin than this," the hostage says. "This is not some undisciplined outfit with a few Kalashnikovs."

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ISIL, which controls large areas of territory in Syria and Iraq, has already executed two US journalists and one British aid worker in recent weeks in what it said was reprisals for US airstrikes against it in Iraq in August.

Cantlie also appears to suggest that US President Barack Obama, long careful to avoid the sort of conflicts his predecessor George Bush pursued, was being sucked into a war he could not win, SITE reported.

"The president once called George Bush's Iraq conflict a 'dumb war,' and couldn't wait to distance America from it when he came into power. Now he's being inextricably drawn back in," Cantlie says.

The hostage said the new Iraqi government, an ally of Shia Muslim power Iran, was waiting eagerly for US intervention to strengthen Iranian influence in the Middle East.

While a strong opponent of ISIL, Iran has sent mixed signals about its willingness to co-operate with the US on defeating the group.

In public, both Washington and Tehran have ruled out co-operating militarily against ISIL.

But in private, Iranian officials have voiced a willingness to work with Washington against the group, though not necessarily on the battlefield.

Source: Agencies