Tim Hetherington, an Oscar-nominated British film director and war photographer, and award-winning US photographer Chris Hondros were killed and two other Western journalists wounded in the besieged Libyan city of Misrata.
Vanity Fair, for which Hetherington was working, confirmed the death of the 41-year-old who covered numerous conflicts and won the 2007 World Press Photo Award for his coverage of US soldiers in Afghanistan.
Hondros, also 41, suffered grave head injuries in the same mortar attack, said medics in the western port city of Misrata, and died hours later from his wounds, Getty Images confirmed to AFP.
Getty "is deeply saddened to confirm the death of Staff Photographer Chris Hondros who has died of injuries while covering events in Libya on April 20th," the agency said in a statement.
Two other colleagues, Guy Martin, a freelance photographer working for Panos, and photographer Michael Brown, working for Corbis, were also wounded in the attack, the agencies confirmed.
Hetherington and Hondros were the second and third journalist killed in Libya in its two-month-old conflict.
President Barack Obama's chief spokesman, Jay Carney, said the US leader was "saddened" to learn Hetherington had been killed, in a statement released before the news of Hondros' death.
"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," Carney said.
Hondros "never shied away from the front line having covered the world's major conflicts throughout his distinguished career and his work in Libya was no exception," Getty said in its statement.
"We are working to support his family and his fiancée as they receive this difficult news, and are preparing to bring Chris back to his family and friends in the United States. He will be sorely missed."
The Liverpool-born Hetherington produced and co-directed the acclaimed documentary "Restrepo," which won a Oscar nomination. Pulitzer Prize-nominated photographer Hondros had covered many of the world's conflict zones over the last decade, working in Kosovo, Angola, Sierra Leone, Afghanistan, Kashmir, the West Bank, Iraq, and Liberia, among other places.