The DPRK's official KCNA news agency only said King had left after a visit "to consult on humanitarian issues" and made no mention of the detainee, Jun Young Su.

"We are very happy to report that Mr. Jun, the American citizen being held in Pyongyang, has been released. We are also delighted that in a day or two he will be back with his wife and family," King said.

The Republic of Korea (RoK)'s Yonhap news agency said Jun had arrived in Seoul.

Jun was arrested last November and admitted committing a crime "against the state" during an investigation, the DPRK's official KCNA news agency reported. The DPRK said on Friday he would be released on "humanitarian grounds.

Media reports say Jun was a businessman from California and that he had been doing missionary work in the DPRK.

King, who led a team of five people to evaluate the DPRK's pleas for food, said he had reached no agreement on food aid.

King's five-day trip was the first official U.S visit to the DPRK since 2009, and comes amid signs the U.S is looking to revive multilateral talks on the country's nuclear program after a hiatus of more than two years.

King added that a field team will remain in Pyongyang until the end of next week.

His visit came as the DPRK’s leader Kim Jong-il wrapped up a secretive visit to China, his third to Asia's biggest economy in just over a year.

The U.S has come under mounting pressure to resume food aid to the DPRK after a U.N report said earlier this year that more than six million people urgently need help in the country.

The DPRK, squeezed by tightened international sanctions for nuclear and missile tests in 2009, has asked about 40 countries for food aid.

The U.S suspended food supplies to the DPRK in 2008 over a monitoring dispute and has said it will only resume them with the RoK's agreement.