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 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.

Xinhua had no further details. North Korea's official KCNA news agency has not reported on the court's decision.

In July, Lim appeared at a news conference in North Korea and confessed that he had travelled to the country 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."

File footage provided by KCNA which cannot be verified by Reuters showed him confessing to crimes against the state.

His church, the 3,000-member Light Korean Presbyterian Church, has said Lim had visited the North more than 100 times since 1997 and has 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."

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

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