WASHINGTON -- South Korea's top nuclear envoy departed Washington on Friday after meeting with US officials amid North Korea's threats to launch military action on Seoul.

Lee Do-hoon, special representative for Korean Peninsula peace and security affairs, boarded a flight home at Dulles International Airport at the end of an unannounced three-day visit to the US capital.

Met by reporters at the airport, he refused to answer any questions on what he discussed with his American counterpart, Deputy Secretary of State Stephen Biegun, or what they agreed to do going forward.

Lee's trip came at a time of heightened tensions on the Korean Peninsula amid North Korea's near-daily threats to punish the South for its failure to stop defectors and activists from sending anti-Pyongyang propaganda leaflets into the North by balloon.

Earlier this week the North blew up an inter-Korean liaison office in its border city of Kaesong and threatened to redeploy troops to border areas.

The US State Department has expressed its disappointment at North Korea's recent actions to sever ties with the South and urged the communist country to refrain from "further counterproductive actions." (Yonhap)