WASHINGTON, Dec 24 (Reuters) - A U.S. court on Monday ordered Pyongyang to pay $501 million in damages for the torture and death of U.S. college student Otto Warmbier, who died in 2017 shortly after being released from a North Korea prison.

Warmbier's parents sued North Korea in April over their son's death. The 22-year-old student died days after he was returned to the United States in a coma, and an Ohio coroner said the cause of death was lack of oxygen and blood to the brain.

"North Korea is liable for the torture, hostage taking, and extrajudicial killing of Otto Warmbier, and the injuries to his mother and father, Fred and Cindy Warmbier," Judge Beryl Howell of the U.S. District Court for the District of Colombia said in her ruling.

Pyongyang has blamed botulism and ingestion of a sleeping pill for Warmbier's death and dismissed torture claims.

Fred and Cindy Warmbier said in a statement they had promised their son justice.

"We are thankful that the United States has a fair and open judicial system so that the world can see that the Kim regime is legally and morally responsible for Otto’s death," the Warmbiers said.

"We put ourselves and our family through the ordeal of a lawsuit and public trial because we promised Otto that we will never rest until we have justice for him," they said. "Today’s thoughtful opinion by Chief Judge Howell is a significant step on our journey."

Howell's ruling was a default judgment, a type of decision entered against a party that does not appear in court. Default judgments against foreign defendants are often difficult to collect.

U.S. courts can compensate default judgment holders by ordering the seizure of funds or other assets located within the country, but that is unlikely in this case because sanctions prohibit North Korea from accessing the U.S. financial system.

The ruling comes at a sensitive time in U.S.-North Korea diplomatic relations, as the two countries negotiate the dismantling of Pyongyang's nuclear weapons program.

Related: Mourners gather to remember Otto Warmbier:

11 PHOTOS Mourners gather to remember Otto Warmbier See Gallery Mourners gather to remember Otto Warmbier Mourners stand out side the art center before a funeral service for Otto Warmbier, who died after his release from North Korea, at Wyoming High School in Wyoming, Ohio, U.S. June 22, 2017. REUTERS/John Sommers II Mourners wait in line outside the art center before a funeral service for Otto Warmbier, who died after his release from North Korea, at Wyoming High School in Wyoming, Ohio, U.S. June 22, 2017. REUTERS/John Sommers II WYOMING, OH-JUNE 21: The town of Wyoming, Ohio prepares for the funeral of Otto Warmbier June 21, 2017 in Wyoming, Ohio. The 22-year-old college student was released from a North Korean prison last Tuesday in a coma after spending 17 months in captivity for allegedly stealing a propaganda poster. (Photo by Bill Pugliano/Getty Images) Sen. Rob Portman, R-Ohio, addresses the media outside the art center before a funeral service for Otto Warmbier, who died after his release from North Korea, at Wyoming High School in Wyoming, Ohio, U.S. June 22, 2017. REUTERS/John Sommers II WYOMING, OH-JUNE 21: Blue and white ribbons are shown at the entrance to Oak Hill Cemetary the day before the funeral of Otto Warmbier June 21, 2017 in Wyoming, Ohio. The 22-year-old college student was released from a North Korean prison last Tuesday in a coma after spending 17 months in captivity for allegedly stealing a propaganda poster. (Photo by Bill Pugliano/Getty Images) Mourners stand outside the art center before a funeral service for Otto Warmbier, who died after his release from North Korea, at Wyoming High School in Wyoming, Ohio, U.S. June 22, 2017. REUTERS/John Sommers II Mourners wait in line outside the art center before a funeral service for Otto Warmbier, who died after his release from North Korea, at Wyoming High School in Wyoming, Ohio, U.S. June 22, 2017. REUTERS/John Sommers II Mourners stand out side the art center before a funeral service for Otto Warmbier, who died after his release from North Korea, at Wyoming High School in Wyoming, Ohio, U.S. June 22, 2017. REUTERS/John Sommers II WYOMING, OH-JUNE 21: A man brings balloons into Wyoming High School, site of tomorrow's funeral for Otto Warmbier June 21, 2017 in Wyoming, Ohio. The 22-year-old college student was released from a North Korean prison last Tuesday in a coma after spending 17 months in captivity for allegedly stealing a propaganda poster. (Photo by Bill Pugliano/Getty Images) Mourners stand out side the art center before a funeral service for Otto Warmbier, who died after his release from North Korea, at Wyoming High School in Wyoming, Ohio, U.S. June 22, 2017. REUTERS/John Sommers II WYOMING, OH-JUNE 21: The town of Wyoming, Ohio prepares for the funeral of Otto Warmbier June 21, 2017 in Wyoming, Ohio. The 22-year-old college student was released from a North Korean prison last Tuesday in a coma after spending 17 months in captivity for allegedly stealing a propaganda poster. (Photo by Bill Pugliano/Getty Images) Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

President Donald Trump has said that Warmbier did not die in vain and his death helped initiate a process that led to a historic meeting this year between Trump and North Korean leader Kim Jong Un.

A student at the University of Virginia, Warmbier was imprisoned in North Korea for 17 months starting in January 2016. He had been visiting the country as a tourist. North Korea state media said he was sentenced to 15 years of hard labor for trying to steal an item bearing a propaganda slogan from his hotel.

(Additional reporting by Jan Wolfe; Editing by Mary Milliken and Cynthia Osterman)

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