WASHINGTON -- US Secretary of State Mike Pompeo paid tribute to Otto Warmbier on Friday, marking the third anniversary of the death of the American college student who was detained in North Korea.

"Today marks 3 years since Otto Warmbier passed away," Pompeo wrote on his personal Twitter account.

"Susan, Nick and I have gotten to know the Warmbiers these past few years -- we are continually amazed by their resolve, patriotism and dedication to justice in light of the most unthinkable loss," Pompeo said, referring to his wife and son. "We must never forget Otto."

Warmbier was detained in Pyongyang in January 2016 for allegedly stealing a political poster from a hotel. He was found in a comatose state when US officials went to secure his release in June 2017.

The University of Virginia student died six days after he was flown back to the US. (Yonhap)