Actor James Gandolfini arrives at the BAFTA Brits to Watch event in Los Angeles, California in this July 9, 2011 file photo.[Photo/Agencies]

James Gandolfini, the burly actor best known for his Emmy-winning portrayal of a conflicted New Jersey mob boss in the acclaimed HBO cable television series "The Sopranos," died while vacationing in Rome, Italy, the network said on Wednesday.

Gandolfini, 51, who began his career in live theater in New York, died of a possible heart attack, HBO spokeswoman Mara Mikialian told Reuters.

Since "The Sopranos" ended its run in 2007, Gandolfini has appeared in a number of big-screen roles, including the espionage thriller "Zero Dark Thirty" and the comedy "The Incredible Burt Wonderstone."

At the time of his death, Gandolfini had been working on an upcoming new HBO series titled "Criminal Justice."