SEOUL - North Korea said on Thursday that American student Otto Warmbier had suffered no torture during his 17-month detention, a day after an Ohio coroner said he died from lack of oxygen and blood to the brain caused by an unknown injury.Sentenced to 15 years of hard labor for trying to take from his hotel an item bearing a propaganda slogan, the University of Virginia student was held by North Korea from January 2016 until his release on June 15.Warmbier died days after arriving in the United States and his parents said that their son had been tortured while in North Korea.North Korea had provided medical care to Warmbier despite his "hostile acts" against the country, and claims of torture are groundless slander aimed at opposing the North, North Korea's foreign ministry spokesman was quoted as saying by the state-run KCNA news agency.