SEOUL (AFP) - South Korea on Wednesday welcomed North Korea's release of a United States citizen, but immediately urged it to free two other American detainees and a South Korean missionary who was arrested on espionage charges.

Mr Jeffrey Fowle, who was detained in April after apparently leaving a Bible in the bathroom of a nightclub in the North, flew out of Pyongyang on a Pentagon plane on Tuesday.

"Our government welcomes Fowle's release," a South Korean Foreign Ministry official said. "We hope other detained figures will be released as soon as possible on humanitarian grounds," the official added, making a particular plea in the case of missionary Kim Jeong Wook.

The North has rejected repeated requests to free Mr Kim, who was arrested last October after he entered North Korea from China.

At a government-arranged news conference in Pyongyang in February, Mr Kim "confessed" to engaging in anti-government activities with the support of South Korea's intelligence agency.

He was sentenced to hard labour for life.

Seoul dismissed the charges, saying Mr Kim was involved in "purely religious activities".

Foreigners arrested in North Korea are often required to make a public confession which can then expedite their eventual release.

Although religious freedom is enshrined in the North Korean Constitution, it does not exist in practice and religious activity is restricted to officially recognised groups linked to the government.