A Christian pastor has gone missing in North Korea, shortly after he was invited to the capital Pyongyang.

Rev Hyeon Soo Lim, 60, of the Light Korean Presbyterian Church in Toronto, Canada arrived in North Korea at the end of January and went missing shortly afterwards.

He was involved in projects including orphanages, nursing homes and food projects from noodle plants to flour mills. Significantly, some of the food projects were linked to Jang Song-Thaek, the late uncle of North Korea's president Kim Jong-Un, via associates.

Jang was executed for treason in December 2012. Speculation that he was condemned to die by being torn apart and eaten by a pack of dogs has never been confirmed.

Rev Chun Ki-Won, the director of Durihana, which helps North Korean refugees, told AFP: "As far as I know, he was asked by officials to come to Pyongyang on January 31 before he went incommunicado. We're worried the invitation to Pyongyang was somehow related to his ties to Jang."

North Korea's constitution preaches religious freedom but in practice there is none. Christians in the North keep their faith a closely guarded secret, for fear of ending up in one of the dreaded penal labour camps. Chun said the information that Lim was missing had come from ethnic Korean missionaries in the US and Canada who are involved in aid projects in the country.

It was at first thought that he was in the standard 21-day quarantine for Ebola virus but fears grew after that period ended with no word.

Lisa Pak of the Light Korean Presbyterian Church told the Toronto Star newspaper that Lim had travelled to North Korea hundreds of times.

Canada advises citizens not to travel to North Korea. Foreign missionaries have been arrested in the past in North Korea, although most have been freed after international intervention.