JOIN USThe New York Times said the journalists, who included two-time Pulitzer Prize winner Anthony Shadid, were last in contact with their editors on Tuesday morning from the town of Ajdabiya.
Also missing were Stephen Farrell -- a reporter and videographer who was kidnapped by the Taliban in 2009 and rescued by British commandos -- and two photographers, Tyler Hicks and Lynsey Addario, the newspaper said.
"We have talked with officials of the Libyan government in Tripoli, and they tell us they are attempting to ascertain the whereabouts of our journalists," Bill Keller, the executive editor of The New York Times, said in a statement.
He said the Libyan government had assured the Times that if the journalists have been captured, they would be released promptly and unharmed.
A Brazilian reporter was freed by government forces in Libya last week, but a journalist from Britain's Guardian newspaper remains missing.
A BBC news team also said last week it had been detained by Libyan security forces, beaten and subjected to mock execution after they were arrested at a checkpoint.
Libyan leader Muammar Gaddafi, in power since a military coup in 1969, lost control of large swathes of Libya in a revolt last month, but since then his security forces have fought back. The Libyan uprising follows popular uprisings that ousted the presidents of Tunisia and Egypt.