Oct 7 (Reuters) - A former Taliban commander already in U.S. custody has been charged with murder and terrorism-related offenses in the deaths of three U.S. troops and an Afghan interpreter and the downing of a U.S. helicopter in Afghanistan in 2008, federal prosecutors in New York said on Thursday. The U.S. Attorney"s Office in Manhattan said Haji Najibullah was charged in a 13-count indictment that was unsealed in federal court. He was previously charged in the 2008 kidnapping of an American journalist and the new indictment supersedes the earlier one and includes charges related to that incident, prosecutors said. Prosecutors said Najibullah served at the time as a Taliban commander in Afghanistan"s Wardak Province bordering the capital Kabul. He was charged in connection with an attack by Taliban fighters under his command on a U.S. military convoy with automatic weapons, rocket-propelled grenades and other explosives, prosecutors said. The attack killed U.S. Army Sergeants First Class Matthew Hilton and Joseph McKay, Sergeant Mark Palmateer and their Afghan interpreter, they said. Najibullah also was charged in connection with an attack by fighters under his command using rocket-propelled grenades that brought down a U.S. military helicopter, prosecutors said. They said no troops died in the attack. A statement from prosecutors said Najibullah was charged with murdering U.S. nationals, providing material support for acts of terrorism resulting in death, hostage-taking, kidnapping and other charges. The statement said the charges carry a maximum penalty of life in prison. The indictment did not name the journalist, but a law enforcement official familiar with the matter told Reuters after the previous indictment that the case involved David Rohde, a former New York Times and Reuters correspondent who was kidnapped by the Taliban in 2008. Rohde, a Pulitzer Prize winner who is now with the New Yorker, escaped in June 2009. Najibullah pleaded not guilty last November in Manhattan federal court after the previous indictment. Najibullah was arrested and was moved to the United States from Ukraine. Prosecutors said he remains in federal custody.