Pentagon chief blasts N.Korea over US student who died

North Korea's treatment of an American student who died after being released from detention in a coma was inhuman and US patience with Pyongyang is running out, Pentagon chief Jim Mattis said Wednesday.

Otto Warmbier, 22, suffered severe brain damage in North Korea and died on Monday following 18 months of captivity in North Korea after he was sentenced to hard labor for stealing a political poster from a hotel.

"To see a young man go over there healthy and, (after) a minor act of mischief, come home dead basically... this goes beyond any kind of understanding of law and order, of humanity, of responsibility towards any human being," Mattis said.

"What you are seeing I think is the American people's frustration with the regime that provokes and provokes and provokes and basically (is) playing outside the rules, plays fast and loose with the truth, that sort of thing."

US President Donald Trump has repeatedly slammed North Korea over its treatment of Warmbier, who died within days of returning to the United States.

Mattis was speaking alongside Secretary of State Rex Tillerson after the two met Chinese officials to discuss North Korea and other regional issues, including China's continued military build up in the South China Sea.

"We had an open and frank dialog about what more can be done in areas of common interest," he said.

Tillerson said "efforts continue" towards securing the release of three more American citizens that are still being "illegally detained" by Kim Jong-Un's regime in Pyongyang.