Journalists covering the chaos in Egypt have become part of the story as dozens of reporters have been harassed, threatened, physically assaulted and arrested since Wednesday in what at least one U.S. official suggested was a broad government effort to suppress coverage of the spreading violence.

ABC News correspondent Brian Hartman reported Thursday that his car was stopped by a group of men at a checkpoint on his way from Cairo's airport to downtown. The car was driven to a compound, where the men threatened to behead him and three ABC colleagues, he reported via Twitter. The group escaped only after ABC cameraman Akram Abi-hanna, who is Lebanese, "appealed to the generous spirit of the Egyptian people, hugging and kissing an elder," Hartman wrote.

On Wednesday, CNN anchor Anderson Cooper was punched about 10 times, apparently by government supporters, as he walked with his cameraman and producer into a clash between factions near Cairo's Tahrir Square.

"We realized there were people in the crowd who were determined to cause trouble. They decided to focus on us as a target of opportunity," Cooper said from Cairo in a phone interview, noting that he took "a couple of pretty good pops in the face."

Added Cooper: "I think anyone with a camera is a target in that square."

On Thursday, Cooper encountered trouble again, as a mob set upon his car and smashed a window. Neither he nor his fellow passengers were injured.

The assaults come amid 11 days of protests throughout Egypt aimed at toppling the nearly 30-year rule of President Hosni Mubarak. The protests have become bloody in recent days as Mubarak's supporters have confronted those seeking his ouster.

There have been no reports of journalists being killed in Egypt's current unrest, but several have reportedly been injured. According to an accounting compiled by ABC News, journalists working for Fox News, CNN, ABC World News and CBS News, among others, have reported facing physical threats and violence.

Secretary of State Hillary Rodham Clinton condemned the attacks on journalists and human rights workers, calling them "unacceptable under any circumstances."

Several news organizations, including The Washington Post, said Thursday that some of their employees had been detained.

Post photographer Linda Davidson was hit by a flying rock while covering a demonstration Wednesday in Cairo, sustaining minor injuries to her scalp. Then on Thursday she was among four Post employees arrested by military police.

Davidson and Post Cairo bureau chief Leila Fadel were held for several hours before being released; they were among a group of about two dozen journalists who were arrested.

Two other Post employees were held longer before being released. One is Sufian Taha, a reporting assistant who is a U.S. passport holder. The other is Mansour el-Sayed Mohammed, an Egyptian passport holder who was hired in Cairo as a driver; he has worked for foreign news organizations in Egypt for three decades.

In some cases, arrest might have been a blessing. While detained, Fadel spoke with other journalists who said their arrests had saved them from pro-Mubarak mobs. Most of the reporters were arrested in downtown Cairo while trying to report about the violence, Fadel said.

"It appears that journalists are being targeted by the Egyptian authorities in a deliberate campaign of intimidation aimed at quashing honest, independent reporting of a transformational event," said Douglas Jehl, The Post's foreign editor. "We are relieved that Leila and Linda have been released . . . and we are alarmed at the continuing threat to the safety of our correspondents and other journalists in Cairo."

Two reporters from the New York Times were held overnight and released unhurt Thursday morning, said Times Editor Bill Keller.

"We also had three other reporters in a car, surrounded by thugs waving knives," Keller said. "Brief but menacing, until military police directed them to safety."

State Department spokesman Philip J. Crowley said there are "strong indications" that the attacks on foreign-aid workers and journalists have been coordinated and planned. "These do not seem to be random events," said Crowley, according to Reuters. There appears "to be an effort to disrupt the ability of journalists" to cover events.

The sheer number of arrests and physical altercations involving reporters strongly suggested an organized campaign to prevent the international media from providing an accurate portrayal of the tumultuous events. TV crews said that in some cases their equipment was seized or damaged.

Several reporters said they saw "spotters" scanning Cairo's high-rise buildings to identify TV crews covering the street demonstrations from the relative safety of apartment and office balconies. Crews were then questioned or arrested.

Journalists working in Egypt have long faced intense scrutiny from security forces on the streets, said Lawrence Pintak, a former Middle East correspondent for CBS News and the author of the newly published book "The New Arab Journalist: Mission and Identity in a Time of Turmoil." But the spread of satellite TV among the Egyptian masses has made the Mubarak government even more hostile toward the foreign and domestic press, he said. "The regime is angry at international journalists and TV in particular," Pintak said, adding that a crackdown is "the natural outgrowth.