NEW YORK - The parents of Otto Warmbier have filed a claim for a seized North Korean cargo ship in a bid to collect a multimillion-dollar judgment in the American college student's death.

Attorneys for the Warmbiers said in a court filing Wednesday they have a right to the assets after North Korea failed to respond to their wrongful-death claim.

The Warmbiers say their son was tortured after being convicted of trying to steal a propaganda poster and imprisoned for months.

He died days after being returned to the U.S. in a vegetative state in 2017. A U.S. judge has ordered North Korea to pay more than $500 million in the Warmbiers' wrongful-death suit.

North Korea has denied mistreating Warmbier.

The U.S. seized the cargo ship in May because it was carrying coal in violation of U.N. sanctions.