Update 3:44 p.m. ET: Secretary of State Hillary Rodham Clinton repeats the U.S. government's position that attacks on journalists are "unacceptable" and that "we condemn them in the strongest terms."
Update 2:44 p.m. ET: Time magazine says it has learned "exclusively" that CBS's Lara Logan and her crew have been detained.
Time did not identify its sources, and CBS would not comment.
Update 2:21 p.m. ET: State Department spokesman P.J. Crowley says that because larger protests are expected Friday, there could be more attacks on journalists in Egypt.
"I don't think that these are random events," he said at the daily State Department briefing.
Update 2:04 p.m. ET: The Washington Post reports that Leila Fadel and Linda Davidson have been released.
The State Department, meanwhile, says Secretary of State Hillary Rodham Clinton may have a statement later today on journalists in Egypt.
Update 1:53 p.m. ET: ABC News has compiled a very useful list of journalists "who have been in some way threatened, attacked or detained while reporting in Egypt."
Update 12:18 p.m. ET: The Committee to Protect Journalists says it has confirmed the detention of 10 journalists. The government says they have not been arrested but were taken into "protective custody."
Vice President Omar Suleiman says "unfriendly media" from "friendly nations" are complicating the military's efforts to keep order, according to state television.
The New York Times reports that Al Jazeera and Al Arabiya are unable to provide live video from Tahrir Square.
White House press secretary Robert Gibbs tells reporters that President Barack Obama has been briefed on the systematic targeting of journalists in Egypt and considers it "completely and totally unacceptable," NBC News' Scott Foster reports after a briefing aboard Air Force One.
Attacks and detentions of journalists — numerous reports, many unconfirmed, blaming the army — spiked beginnig overnight:
• Al Jazeera says three of its reporters reporters are in custody.
• The Washington Post reports that its Cairo bureau chief, Leila Fadel, and photographer Linda Davidson, have been detained.
• Two New York Times journalists are reported to have been arrested.
• The Globe and Mail of Canada reports that two correspondents and a driver were detained.
• Polish state television said two of its crews were detained in Cairo. One crew, made up of two cameramen, has been released; the status of the other, a reporter and two assistants, is unknown.
• The Russian channel Zvezda says a correspondent and a cameramen were detained and held overnight Tuesday before being released.
State Department spokesman P.J. Crowley tweeted: "There is a concerted campaign to intimidate international journalists in Cairo and interfere with their reporting. We condemn such actions."