The nine-member U.S. delegation led by former New Mexico governor Bill Richardson and Google Executive Chairman Eric Schmidt left here Thursday after a four-day "private humanitarian visit" to the Democratic People's Republic of Korea (DPRK).

"It is a productive and successful trip," Richardson told Xinhua, adding that they "had a good opportunity with the Korean people, and talked about the expanding of internet, cellphones, and more communication."

Unlike Richardson, Schmidt refused to answer any questions during the whole visit.

During the visit, the delegation met with DPRK Foreign Ministry officials, visited the electronic library of Kim Il Sung University and the Korean Computer Center, and paid visit to the Kumsusan Palace of the Sun.

Upon arrival on Monday, Richardson told Xinhua that they were interested in the economic and political situation in the DPRK, and believed in the importance of dialogue.

Richardson reportedly expressed his concern about the DPRK's missile launch in meeting DPRK officials and called for humane treatment of an American detained in the country.

But he did not mention whether he met Kenneth Bae, a Korean-American tour agent detained in early November for "committing a crime against the country."

DPRK's official news agency KCNA said on Dec. 21 that Bae has admitted the crime and would face legal action.

Richardson announced his DPRK visit together with Schmidt in December, but postponed the trip as requested by the U.S. State Department, the former governor said upon his arrival.