Islamic State militants have threatened to target the White House and kill US troops in a new slickly made video response to Barack Obama's campaign to "degrade and destroy" the organisation.

The video, in the style of a blockbuster movie trailer for what is "coming soon", purports to show a masked man apparently about to shoot kneeling prisoners in the head. Towards the end of the clip there is shaky footage of the White House filmed from a moving vehicle, suggesting the building is being scoped out for attack.

It was released on Tuesday after US defence chiefs suggested that American troops could join Iraqi forces fighting Isis, despite Obama's assurance that US soldiers would not be engaged in fighting on the ground.

Screengrab purporting to show a militant apparently about to shoot kneeling prisoners in the head. The perspective and focus however suggests that it may be two images spliced together

The only words on the 52-second clip are those of Obama making that pledge. "American combat troops will not be returning to fight in Iraq," it quotes him saying. This comes directly after footage of US troops being shot at, injured and taken away in an armoured vehicle, threatening what will happen if troops are redeployed to Iraq.

The video was released by the al-Hayat Media Centre, Isis's English-language propaganda arm. It includes the now-familiar high-production hallmarks of an Isis video, including super-slow motion footage of jihadis in combat, jump-cutting, and CGI explosions.

Professional film editors invited to view the video by the Guardian however cast doubt on the authenticity of some scenes, in particular footage purporting to show a US soldier being shot that appears to have been taken from a video game and images appearing to show prisoners being shot that could have come from two separate sources spliced together.

The video purports to be a trailer for film entitled Flames of War with the strapline "Fighting has just begun".

A still from the latest Islamic State video. Photograph: YouTube

It shows US tanks and positions being attacked by jihadis using shoulder-launched missiles. It also includes an image of the "Mission Accomplished" banner that was part of the backdrop to George Bush's infamous speech on an aircraft carrier after the 2003 US-led invasion of Iraq. There is also footage of Bush's defence chief, Donald Rumsfeld, on a tour of Iraq.

Despite its slick production, experts in film and advertising have suggested the video threat would not require huge expertise or budget.

"These sort of effects are relatively simple to do nowadays. There are iPhone apps that add explosions and look quite real," said Luke Jacobs, an executive producer in TV commercials at Friend Productions.

"The video is slickly done and they have spent some time on it, but it's not something that would require access to a big post-production house. I'd say it's more likely been done by a guy with a laptop. It looks like there might be someone on team Isis who used to work at a TV network or knows his way around visual effects software, a compositor like Nuke or Adobe After Effects."

Flames of War Isis video. Photograph: YouTube

The video came as the Pentagon released details of more air strikes south-west of Baghdad and north-west of Irbil on Monday and Tuesday.

In a statement, the US military's central command said: "In total, two air strikes north-west of Irbil destroyed an Isil [Isis] armed truck and an Isil fighting position, while three air strikes south-west of Baghdad damaged an Isil truck and destroyed an Isil anti-aircraft artillery piece, a small Isil ground unit and two small boats on the Euphrates river that were re-supplying Isil forces in the area.

It said the strikes were conducted as part of US efforts to help an Iraqi offensives against Islamic State militants. The US has conducted 167 air strikes in Iraq since it launched the current campaign on 8 August.

Earlier, General Martin Dempsey, the chairman of the joint chiefs of staff, told the Senate armed services committee that he could see himself recommending the use of some US military forces now in Iraq to embed within Iraqi and Kurdish units to take territory away from Isis.

"If we reach the point where I believe our advisers should accompany Iraqi troops on attacks against specific [Isis] targets, I will recommend that to the president," Dempsey said, preferring the term "close combat advising".

It was the most thorough public acknowledgement yet from Pentagon leaders that the roughly 1,600 US troops Obama has deployed to Iraq since June may in fact be used in a ground combat role, something Obama has directly ruled out, most recently in a televised speech last week.

Dempsey, who has for years warned about the "unintended consequences" of Americanising the Syrian civil war that gave rise to Isis, said he envisioned "close combat advising" for operations on the order of taking Mosul, Iraq's second largest city, away from Isis.

Obama's prohibition on ground forces in a combat role was less ironclad than the president has publicly stated, Dempsey suggested.

"At this point, his stated policy is we will not have US ground forces in direct combat," Dempsey said, to include spotting for US air strikes. "But he has told me as well to come back to him on a case-by-case basis."