The images of North Korean military hovercraft landing on a desolate beach were supposed to portray a disciplined, combat-ready army ready to launch or repel an attack at a moment's notice.

As South Korea and the US continued their controversial joint military exercises in the region, the North's official news agency this week distributed photographs showing the communist state playing war games of its own.

The hovercraft image, however, may have been doctored to make the exercise appear more menacing than it really was.

The photo, which was widely carried in the international media on Tuesday, shows several hovercraft coming ashore at an undisclosed location on North Korea's east coast the previous day.

A couple of dozen troops units of the Korean people's army and navy can be seen running ahead of one of the craft, apparently to be "repelled" by soldiers positioned behind a bank at the edge of the beach.

Writing in the Atlantic magazine's In Focus section, Alan Taylor said he believed the photo, issued by the Korean Central News Agency and distributed to media organisations by Getty Images, had been digitally manipulated.

Taylor said several of the eight hovercraft in the photo appear to be digital clones, speculating that at least two of them had simply been copied and pasted elsewhere. Another craft raised suspicions due to its "soft edges, lack of visible wake, and color oddities".

Two of the near hovercraft, boxed in red, appear to be the same hovercraft, digitally manipulated. It appears that two in the distance, boxed in purple, are also unnaturally similar Photograph: /

Resizing one of the hovercraft so they are the same size, the similarities become even more evident Photograph: /

Again resizing the hovercraft that are in the foreground, the similarities are obvious. On the right hand image, at the front of the hovercraft missing pixels are clearly visible Photograph: /

This isn't the first time that North Korea has been accused of doctoring images for propaganda effect.

A photograph taken at the December 2011 funeral of the state's previous leader, Kim Jong-il, was allegedly altered after the original showed half a dozen men, who appear to be TV journalists, looking away from the main spectacle.

In the manipulated version, the errant men, their camera and footprints had been digitally removed, giving the impression that all eyes were on Kim's funeral cortege as it passed ranks of mourners in the capital, Pyongyang.

The discrepancy was only noticed because the men were clearly visible in a photo taken at almost exactly the same moment by Japan's Kyodo news agency.