A US judge Thursday sentenced notorious Boston underworld kingpin and reputed FBI informant James "Whitey" Bulger to two life terms for 11 murders and dozens of other criminal charges.

Judge Denise Casper added extra five years to his sentence and ordered Bulger to pay $19 million in restitution for his victims.

At the age of 84, Bulger -- a fugitive for 16 years before his arrest in California in 2011 -- is likely to die in prison.

Casper told the US district court in Boston that the nature of Bulger's crimes spanning 40 years was "unfathomable."

"The motivation of your entire criminal history is based on money. It takes no business acumen to stick a gun in somebody. It's what anyone can get at the end of gun," she said.

Casper dismissed Bulger's complaints of a sham trial.

"Call it what you want, but in my estimation you received a fair trial," she said.

When asked if he understood, Bulger uttered just one word: "Yes." His lawyers said that he would appeal the conviction.

"I think Jim is pleased that he held to his principles and chose not to react. He is very disciplined," his lawyer Jay Carney told reporters.

A jury in August found Bulger guilty on 31 counts, including 11 of the 19 murders for which he had been charged. The only count for which he was not convicted was an extortion charge.

Besides murder, Bulger was also accused of money laundering and arms trafficking.

Bulger attorney Hank Brennan said the mobster would appeal the conviction.

The trial, which began June 4, featured 72 witnesses, 840 exhibits and chilling testimony worthy of a pulp novel.

It heard harrowing tales of teeth being pulled from the mouths of murder victims to foil their posthumous identification and the fatal strangulation of a mobster's girlfriend who "knew too much."

Bulger refused to testify at his trial, saying the proceedings were "unfair and a sham" because it would not recognize what he claimed was immunity from prosecution given by federal agents.

Bulger has always denied having been an FBI informant, but close links between some FBI agents in Boston and Bulger's Winter Hill Gang in the 1970s and 1980s have been well documented.

Former FBI agent John Connolly is in prison after being convicted in 2002 of effectively becoming a member of the gang.

Bulger provided the inspiration for Jack Nicholson's mob boss character in Martin Scorsese's Oscar-winning 2006 gangster film "The Departed."

The trial was clouded by the death of former south Boston liquor store Stephen Rakes, 59, who had been expected to testify against Bulger having claimed he was a victim of extortion.

Rake's body was discovered in mid-July in Lincoln, Massachusetts where the local district attorney said there had been no obvious signs of trauma.