The woman's gory wounds had vanished on the large image that wrapped around the New York Daily News on Tuesday, despite the photograph appearing unedited online and in other publications in the US.

In the original photo, taken by John Tlumacki of The Boston Globe, the woman is shown lying in a pool of blood while a man crouches over her, attempting to help. A large wound is clearly visible on her leg as she lies with her hand covering her eyes.

It was one of several graphic images taken in the moments after the twin blasts that killed three people and wounded more than 175 near the finish line of the famous race.

The photographic manipulation now has ignited debate about the point at which images become too gruesome for media organisations to publish.

The New York Daily News' photoshopped image was first highlighted on the American Copy Editors Society website by blogger Charles Apple, who wrote: "If you can't stomach the gore, don't run the photo. Period."

A spokesman for the New York Daily News initially declined to comment on the newspaper's editorial decision-making when contacted by New York-based news website Capital.

However the spokesman, Ken Frydman, later confirmed that the photograph had been manipulated.

"The Daily News edited that photo out of sensitivity to the victims, the families and the survivors," he said.

"There were far more gory photos that the paper chose not to run, and frankly I think the rest of the media should have been as sensitive as the Daily News."

The decision to alter the image came "straight from the top of the masthead", according to unnamed sources who spoke to Capital.

"Photographers and editors are so embarrassed and saddened by this," said one source.

Another person who claimed to be a photographer at the New York Daily News wrote anonymously on the original blog post that they were "completely mortified".

"My colleagues are furious. It is, indeed, inexcusable," the person wrote.

Sydney Morning Herald editor-in-chief Sean Aylmer said editors walked a fine line when selecting images to run alongside a story such as the Boston Marathon bombings.

"You can't filter the news, no matter how bad it is," Aylmer said.

"Generally you should be able to use any photo you want. The big caveat is taste. When you know that your newspaper or digital platforms are being seen by lots of people, from eight-year-olds to 80-year-olds, you don't want to turn them off. Therefore we tend not to put a lot of blood on the front."

He said one front-page image that ignited debate was in the aftermath of September 11 when the Australian Financial Review showed a man jumping from the burning World Trade Centre.

"Some people thought that was the wrong thing to do for the front page of a national newspaper, but it was probably one of the most iconic photos of 9/11, and it was the news," Aylmer said.

Professor Alan Knight, the head of the graduate school of journalism at the University of Technology, Sydney, said graphic images of blood and gore were commonly published in the media in parts of Asia.

"In the west we tend to be more careful, and of course there are broadcasting guidelines in Australia and people do tend to complain a lot about these sort of things being portrayed," he said.

"But I think basically digitally altering these sort of photographs [like done in the New York Daily News] is insulting the intelligence of the readers."

He said on the same day as the Boston Marathon bombings, more than 30 people were killed in and around Baghdad, but images of that violence were not broadcast.

While it was more difficult to access information and photographs from Baghdad, editors were also making judgment calls.

"If you look at Boston, it's in a country that Australia identifies with, and the images are easily accessible. This happened in the middle of a city, lots of journalists were present with excellent internet links. Not only journalists, there's people with mobile phones. That's the sort of incident that's likely to be covered," he said.

"Maybe the editors made a judgment that we don't culturally identify with the people in Iraq quite as much as we do with those in Boston."