A Korean-American man who says he is being held in North Korea was a Christian pastor in the US, according to a North Korean defector who met him and traveled with him in 2007.

CNN reported on Monday from North Korea that it had been given access to a man claiming to be an American, who identified himself as Kim Dong Chul, and who said he had been arrested in North Korea on spying charges.

He appealed for help from the United States or South Korea to rescue him.

A US State Department official declined to comment on the report about Kim, saying that speaking publicly about specific cases of detained Americans can complicate efforts to get them released.

If confirmed, Kim, who CNN said was 60 and formerly of Fairfax, Virginia, would be the second Western citizen known to be held in North Korea. The other is Korean-Canadian pastor Hyeon Soo Lim, sentenced last month to hard labour for life. CNN revealed that he spends up to eight hours a day digging holes and has no contact with other prisoners.

CNN was given access to both men this week, just days after isolated North Korea conducted its fourth nuclear test.

A North Korean defector, Ma Young-ae, told Reuters on Tuesday that she had met Kim in the United States.

"He told the churches that he was a missionary working on North Korea and sending stuff from China into the North to help poor North Koreans," Ma said, recalling Kim making speeches around California and Virginia in 2007 and seeking donations.

'Shocked'

Ma, who is working as a missionary based in the New York area under what she said was security protection, described Kim as a Korean-American.

"I was shocked to see his face on TV," she added.

Kim had told her he was sending medical aid into North Korea and going in and out of Rason, a North Korean special economic zone bordering China, she said.

A photograph from a small Korean-American online publication showed a man it said was Kim talking at an unidentified church in the Washington, DC area.

Ma said Kim had once asked her and her husband to come to China to work with him but she had declined.

A pastor named Park Simon, who also accompanied Ma and Kim to several church gatherings in the United States, told Voice of America that Kim visited North Korea and called him from Pyongyang about four years ago.

Kim told CNN he had spied on behalf of "South Korean conservative elements" and had been arrested in October.

The other foreigner known to be in detention in North Korea, and who CNN was also given access to, is Hyeon Soo Lim, a South Korean-born Canadian who was the head pastor at one of Canada's largest churches.

Lim has been held by the North since February. Lim, who was 60 at the time of his arrest, was sentenced in December for attempting to overthrow the North's regime.

Canada's Prime Minister Justin Trudeau said after his sentencing: "The issues of North Korea's governance and judicial system are well known. We certainly hope to be able to engage with this individual and stand up for his rights."

François Lasalle, a spokesman for Canada's Department of Global Affairs, said: "Canada is dismayed at the unduly harsh sentence given to Mr Lim by a North Korean court, particularly given his age and fragile health."

Additional reporting by Reuters.