Editors at the newspaper said they last heard from the journalists on Tuesday as they were covering the retreat of rebels from the town of Ajdabiya. Libyan officials told the newspaper they are trying to locate the four, executive editor Bill Keller said in a statement.
"We are grateful to the Libyan government for their assurance that if our journalists were captured they would be released promptly and unharmed," Keller said.
The missing journalists are Pulitzer-Prize-winning reporter Anthony Shadid, the newspaper's Beirut bureau chief; Stephen Farrell, a reporter and videographer; and photographers Tyler Hicks and Lynsey Addario. In 2009, Farrell was kidnapped by the Taliban and later rescued by British commandos.
"Their families and their colleagues at The Times are anxiously seeking information about their situation, and praying that they are safe," Keller said.
The White House on Wednesday urged the Libyan government to refrain from harassing or using violence against journalists. Obama spokesman Jay Carney said the United States is firm in its belief that journalists should be protected and allowed to do their work.
Pro-Gadhafi forces have largely gained control of Ajdabiya after two days of relentless shelling but still face pockets of resistance in the city of 140,000 people. Habib al-Obeidi, a doctor at Jalaa Hospital in Benghazi, said that a colleague in Ajdabiya had told him 25 people were killed when pro-Gadhafi forces opened fire on civilian cars fleeing the city. That report could not be independently confirmed.
The breakdown in rebel defenses in Ajdabiya threatened to open the gateway to the long stretch of eastern Libya that has been in the control of the opposition, including Benghazi, Libya's second-largest city and the de facto capital of the opposition.
In September 2009, Farrell and Sultan Munadi, an Afghan journalist and interpreter who worked regularly with the Times and other news organizations, were taken hostage when they went to cover the aftermath of a NATO airstrike that killed scores of civilians in northern Afghanistan.
Munadi and a British commando died in the raid that rescued Farrell, a Briton. British forces said they had to leave Munadi's body behind because they were coming under such heavy fire.
In 2008, New York Times reporter David Rohde was kidnapped while trying to make contact with a Taliban commander in Afghanistan. Rohde and an Afghan colleague escaped in June 2009 after seven months in captivity, most spent in Taliban sanctuaries in Pakistan.