The US military has been forced to deny claims that one of its warplanes was shot down over Iraq by Islamic State after the group posted reports a US jet had crashed landed in Anbar province.

"There is no truth to reports of Isil downing a US aircraft near Anbar," US central command tweeted through an official Twitter account. "All US and coalition aircraft accounted for at this time," it added.

Islamic State made the claims over the downed US aircraft through its propaganda outlet al-Amaq news agency. The terror group posted messages in Arabic and English saying the jet had been shot by its fighters and its pilot killed.

"The crew of the US warplane that was shot down by Islamic State fighters near Ayn Asad airbase is dead," Amaq posted on 25 July.

The Islamic State, which captured vast swathes of territory across Iraq in the summer of 2014, has been on the back foot in the country following an increase in pressure from US and coalition forces.

Mosul, Islamic State's de-facto capital in Iraq, is the last major urban centre held by the group in the country. Over the last year, the coalition has clawed back IS-held ground, retaking the cities of Ramadi and Fallujah.

However, as the US and its allies have waged a more effective ground war against IS, the group has changed its strategy to focus more on insurgency tactics. In the worst assault in the country since the US invasion in 2003, a massive suicide attack in Baghdad's bustling commercial area of Karada on 2 July killed at least 186.