MISRATA, Libya - Two Western photojournalists, including an Oscar-nominated film director, were killed Wednesday in the besieged city of Misrata while covering battles between rebels and Libyan government forces. Two others working alongside them were wounded.

British-born Tim Hetherington, co-director of the documentary "Restrepo" about US soldiers on an outpost in Afghanistan, was killed inside the only rebel-held city in western Libya, said his US-based publicist, Johanna Ramos Boyer. The city has come under weeks of relentless shelling by government troops.

Chris Hondros, a New York-based photographer for Getty Images, was also killed. His work appeared in major magazines and newspapers around the world, and his awards include the Robert Capa Gold Medal, one of the highest prizes in war photography.

Many circumstances of the incident were unclear. A statement from Hetherington's family said he was killed by a rocket-propelled grenade.

The Washington Post reported that the journalists had gone with rebel fighters to Tripoli Street in the center of Misrata, scene of the some of the most intense recent fighting in the city.

After an ambulance rushed Hetherington and Martin to a triage tent, an American photographer whose bulletproof vest was splattered with blood implored the drivers to go back for more victims, the Post reported.

Hetherington was bleeding heavily from his leg and died about 15 minutes after he reached the triage facility, while Hondos died after suffering a severe brain injury from shrapnel, the Post reported.

In Washington, the White House expressed sadness over the attack and called on Libya and other governments to take steps to protect journalists.

"Journalists across the globe risk their lives each day to keep us informed, demand accountability from world leaders and give a voice to those who would not otherwise be heard," press secretary Jay Carney said.