North Korea's highest court has sentenced a South Korea-born Canadian pastor to hard labour for life for subversion, China's official news agency Xinhua has reported.

Hyeon Soo Lim, the head pastor at a Toronto church that is one of Canada's largest, has been held by North Korea since February. He had appeared on North Korean state media earlier this year confessing to crimes against the state.

North Korea's supreme court said Lim had attempted to overthrow the North Korean government and undermine its social system with "religious activities" for the past 18 years, Xinhua reported.

The court held that he fabricated anti-North Korean propaganda as part of a US and South Korean-led "human rights racket" against the country, according to Xinhua.

The court said Lim confessed to helping people defect from North Korea and said he had met the US ambassador to Mongolia regarding the plans, Xinhua reported.

The US embassy in Mongolia had no immediate comment when contacted by Reuters.

Most defectors fleeing isolated, repressive North Korea travel to South Korea via China and Southeast Asia, although it is possible to defect via Mongolia.

The Canadian government also declined to comment.

A church spokeswoman did not immediately respond to an emailed request for comment late in the Canadian day.

North Korea's official KCNA news agency had not reported on the court's decision.

Hands clasped

The Associated Press showed images of Lim, wearing a padded winter jacket with his hands clasped together, being led to sentencing in Pyongyang on Wednesday by two security personnel.

North Korea has previously sentenced a Korean-American missionary, Kenneth Bae, to 15 years of hard labor but released him last year after holding him for two years.

In July, Lim appeared at a news conference in North Korea and confessed that he had traveled there on the pretext of humanitarian work and gathered information that he used in sermons outside the country to drive the regime to a collapse "with the love of God".

His church, the 3,000-member Light Korean Presbyterian Church, has said Lim had visited the North more than 100 times since 1997 and had helped establish an orphanage and a nursing home there.

Lim has lived in Canada since 1986 and is a Canadian citizen.

His church said in March that Lim, who was 60 at the time, has "a very serious health problem, very high blood pressure, he's on a prescription, and his family is anxious to send medicine".

He is the only Western citizen known to be held currently in North Korea.

Both North Korea and neighbouring China have clamped down on Christian groups in recent years.

Last year, Pyongyang released three detained Americans, including Bae and another man who had left a copy of the Bible at a club. It freed a South Korean national with a US green card in October this year after holding him for six months.

In June, the North's highest court sentenced two South Koreans accused of spying for Seoul to hard labour for life. The pair are among three South Koreans known to held by the North.