Former US president, Mr Jimmy Carter, left North Korea on Friday after achieving the release of a US man who had been imprisoned there, the state-run Korean Central News Agency said.

Carter flew to Pyongyang on Wednesday to lobby for the release of Aijalon Mahli Gomes, 30, who was arrested in January and sentenced in April to eight years of hard labour for illegally entering North Korea from China.

During his visit, Mr Carter met with North Korea's number two leader, Kim Yong Nam, who "expressed the will of the North Korean government for denuclearization of the Korean Peninsula and resumption of the six-party talks", the news agency said, referring to talks aimed at ending North Korea's nuclear weapons programme, in which both the US and North Korea are involved.

Carter, who won the Nobel Peace Prize for his post-presidential humanitarian work, left North Korea accompanied by Gomes, who was released in a humanitarian gesture by North Korean leader Kim Jong Il, said the Carter Center, a Carter-founded non-governmental organisation, which works on human rights issues.

Gomes had been working as an English teacher in South Korea. The reason he crossed the border remained unclear, but he was believed to be a Christian activist, and in South Korea he had protested against North Korea's poor human rights record.

Gomes was to return on Friday to Boston to be reunited with his family, the Carter Centre said.

North Korea also said the release was made on humanitarian grounds.

Carter's visit followed a similar one a year ago by another former US president, Mr Bill Clinton, who secured the release of two journalists who had also been sentenced to forced labour for illegal entry into North Korea.

Both Mr Carter and Mr Clinton said they travelled to North Korea on private visits. The US and North Korea, enemies during the 1950-53 Korean War, continue to be diplomatic rivals and have no official ties.

The US government welcomed Gomes' release but stressed Carter's visit was a private one and was not suggested or arranged by the US government.

Mr Philip Crowley, a spokesman for the US State Department, said the US government agreed with Carter's decision to accept the release after determining that Gomes required immediate medical care in the United States.

He did not release details about the health of Gomes, who looked trim Friday as he boarded a plane to leave North Korea.

Although the US and North Korea do not have official ties, they do hold talks via the six-nation denuclearization negotiations, which also involve China, South Korea, Japan and Russia. However, those talks have been stalled since the end of 2008.

North Korea has repeatedly said recently it is willing to return to the table but has not proposed a concrete date or venue.

Although Carter's visit was a private one, observers said he might also act as a mediator between Washington and Pyongyang as he did 16 years ago in a past conflict about the communist country's nuclear ambitions.

In 1994, during his first trip to North Korea, which was also termed a private mission, Carter helped restart nuclear talks that led to an agreement, in which North Korea agreed to eventually dismantle its nuclear programme in exchange for fuel and diplomatic concessions. That pact has since collapsed.

Carter had been expected to meet Kim Jong Il during his latest visit, but he arrived a few hours before Kim left North Korea via train on a trip to China, his second in three months, according to South Korean reports.