Meanwhile, amateur pictures of the bombing began popping up on Flickr, a photo swapping Web site, at the same time mainstream news organizations were announcing the tragedy.

Welcome to the world of citizen newsgathering, where technology and the age-old desire to communicate hot information, be it hard news or soft gossip, are converging and forcing traditional news outlets to dramatically change the way they cover big news events.

It got a big push from the Sept. 11, 2001, terrorist attacks, and has gathered more steam as camera phones have become more ubiquitous, blogs have become more numerous, and mainstream media outlets have gotten more Web-savvy.

''September 11 marked an important date in the history of how people got information when a major news event happened,'' said Rich Gordon, director of the new media program at Northwestern University's Medill School of Journalism.

In the wake of the attacks, more people increasingly sought - and shared - information on the Internet. Do-it-yourself journalism became more popular on the Web, while Americans helped cope with the crisis by posting their own reactions - and reading those of others - on both mainstream and non-mainstream media sites.

''Four years later, there are even more sources [of information] and even more familiarity with the variety of sources that exist,'' Gordon said. ''And in that four-year time period, there has been an explosion of media production tools in the hands of people.''

One of those tools is the rise of Web logs, or blogs, Web sites where people can post their opinions and pictures.

Software developments in the past few years have made it easier to create Web sites or post pictures on existing sites, Gordon said. ''To post a photo on Flickr is a piece of cake,'' he added.

Flickr was launched in early 2004, and was purchased by Internet colossus Yahoo earlier this year. Flickr users can share photos on all sorts of subjects, and big news often drives surges in postings.

When a giant tsunami washed through South Asia in December, killing tens of thousands of people, Flickr was inundated with thousands of pictures, said Caterina Fake, a Flickr co-founder.

The first pictures from London were posted on Flickr at the same time workers at its California data center were hearing about the bombings through the mainstream media, Fake said. Within 14 hours of the blasts, there were over 450 pictures posted.

Five of them came from James Cridland, including one showing ambulances lined up outside the King's Cross subway station, one of the bombing sites. At least three British blogs picked up the picture off Flickr.

Cridland, head of new media for Virgin Radio in London, normally commutes into work on the subway route that got bombed. But Thursday, he biked to his office, stopping when he noticed a congregation of police near the station.

''I took a couple of snaps on the off-chance it was something exciting,'' Cridland said in an e-mail. When he got to work, he posted his pictures.

Cridland got the bug to shoot and share pictures a few months ago when he took a business trip to South Korea. Unable to stay in contact with his family via cell phone, he kept in touch by posting photos on Flickr. It was fun, so now he has made a habit of it.

He is what Scott Shamp, director of the University of Georgia's New Media Institute, would call a new sort of ''embedded reporter.'' His turf, like all citizen-embedded reporters, is just about anything and everything in the world around him.

These reporters' tools include digital cameras, which at $100 for low-end models are now widely affordable.

And more than ever, it has been the camera phone.

It was a novelty in 2001, making up a sliver of all cell phone sales. Nowadays, at least 75 percent of all phones shipped by wireless phone giant Motorola Inc. are equipped with cameras. Today, camera phones outsell digital and film cameras combined.

''The world of these mobile communications devices has so radically changed,'' Shamp said. Just a few years ago, ''who would've carried a camera with them on a daily basis?''

Video cell phones are the next wave in wireless hardware. CNN used a cell phone clip for the first time Thursday to cover a major news event, said Jonathan Klein, president of CNN/U.S.

The clip was originally obtained by Britain's Sky TV, which made it available to all news organizations, Klein said.

The pictures taken by the new breed of accidental photojournalist are different than those taken by professional news photographers. That's partly because they're simply not as skilled as pros.

But it's also because they are taking ''personal'' pictures, Shamp said. Their images are more from the vantage point of an ordinary person. ''This is a medium of raw emotion,'' Shamp said.

Major media organizations are increasingly reaching out to such citizen journalists.

After Thursday's bombing, the Web site of Britain's Guardian newspaper had links to Flickr galleries and to blogs featuring first person bombing accounts.

The BBC's Internet site had a prominent posting to readers saying, ''We want your pictures.'' Below it was ''Eyewitness Accounts,'' a link to bombing pictures sent in by readers.

''Mainstream media are coming to realize they are not islands anymore,'' said Northwestern's Gordon.