Children find violence on TV news more disturbing than anything else on screen, a study has suggested.
Children said 11 September was the most violence they had seen on TV
Children could easily tell the whether violence was real or not - and showed "little lasting impact" from violence they knew was fictional, it said.
But major news stories - such as 11 September - had the "greatest effect" on them, the report concluded.
Screen watchdogs and the BBC surveyed children between nine and 13 to find out how they viewed violent scenes.
The report said they accepted far-fetched TV dramas and cartoon-like film violence more easily because they knew they were made up.
Few major news stories had an impact because many children thought most were "boring".
But big stories, such as 11 September, war in Iraq and the killing of schoolgirls Holly Wells and Jessica Chapman, did get their attention.
Children can tell the difference between violence in news and soaps
Those events made children feel "threatened" and "personally vulnerable", the report said.
"In turn, this can lead to genuine anxieties and changes in
behaviour," the report said.
Children are most worried by scenes involving other children or that are closer to home - while other, more remote stories have less impact, it said.
And unlike adults, children did not need to see acts of violence - but were more concerned by the consequences - the study said.
The report said the findings presented "a real challenge to broadcasters".
The Independent Television Commission (ITC), which was among the groups that compiled the report, said news broadcasters may need to consider giving warnings about potentially disturbing reports.
Professor David Morrison from the Institute of Communication Studies at the University of Leeds said for children, said the events of 11 September were "almost universally described as the most violent images they had seen on television".
"Children in the sample saw a high level of violence in the news, whereas adults in the previous study considered there to be little violence," he said.
"The news was more violent for them than for adults because it was real and what was real might become real for them."
The report was compiled by the ITC, the Broadcasting Standards Commission, the British Board of Film Classification and the BBC.
It also said children had the impression that the world was more violent now than in their parents' day.