Reuters has dropped a long-serving Lebanese photojournalist covering the Israeli assault on the country after an investigation by bloggers revealed an image had been digitally manipulated to increase the apparent severity of a bombing raid.

The photograph, filed by Adnan Hajj, showed black smoke billowing from burning buildings in a Beirut suburb on Saturday, but was immediately questioned in a post by Washington DC, graphic artist Jeff Harrell, writing: "By all appearances, it looks like Adnan Hajj used the clone stamp tool about 63 zillion times to paint more smoke into the sky above Beirut."

Other right-wing bloggers and a community of professional photographers poured over the image, suggesting that wrecked buildings, too, had been artificially replicated to increase the appearance of damage in the city. Reuters killed the image on Sunday morning in response to the concerns.

"Reuters has discussed the incident with the photographer. The photographer has denied deliberately attempting to manipulate the image, saying that he was trying to remove dust marks and that he made mistakes due to the bad lighting conditions he was working under," said Moira Whittle, the head of public relations for Reuters.

"This represents a serious breach of Reuters' standards and we shall not be accepting or using pictures taken by him. As soon as the allegation came to light, the photograph, filed on Saturday, 5 August, was removed from the file and a replacement, showing the same scene, was sent. The explanation for the removal was the improper use of photo-editing software."

Some of the blogs, including Charles Johnson's Little Green Footballs, which previously helped force CBS News to retract a story about President Bush's war record, assembled close-ups and animated images to illustrate the manipulation.

"It's so incredibly obvious," Mr Johnson wrote. "Smoke simply does not contain repeating symmetrical patterns like this, and you can see the repetition in both plumes of smoke."

Mr Hajj has worked for Reuters since 1993 on a freelance basis - with a two-year break between 2003 and 2005. His photography was questioned earlier last week by online observers scrutinising his images of a rescue worker retrieving the body of a child killed in Israel's heavy bombardment of Qana.

Finding the picture was part of a series of images taken over several hours by agency photographers, critics speculated that the body may have been paraded and posed for cameras by Hezbullah associates, an allegation later rejected by agencies.

Free daily newsletter

If you like our news and feature articles, you can sign up to receive our free daily (Mon-Fri) email newsletter (mobile friendly).