North Korea on Monday released video footage of a detained Canadian pastor attending church in Pyongyang and admitting to unspecified subversion charges levelled after his arrest in January.

Uploaded to the North's official website, Uriminzokkiri, which distributes news and propaganda from state media, the video showed Reverend Hyeon Soo Lim attending a Sunday service at the capital's Pongsu Church.

"I committed the gravest crime of insulting and defaming the top dignity and the leadership of the republic," Lim, using a microphone, said in an address to the small congregation that included a number of foreigners.

The pastor from the Light Korean Presbyterian Church in Toronto was detained by North Korean authorities in January after arriving from China.

A few days ago, North Korean state media said Lim had admitted to carrying out "subversive plots" and attempting to "build a religious state" in North Korea.

Pyongyang views foreign missionaries with deep suspicion, though it allows some to undertake humanitarian work.

A number of Christian missionaries -- mostly ethnic Koreans who are US citizens -- have been arrested in the past with some of them only allowed to return home after intervention by high-profile US political figures.  

Although religious freedom is enshrined in the North's constitution, it does not exist in practice and religious activities are restricted to officially recognised groups linked to the government.

In the video released on Monday, Lim, clad in a dark suit and looking down at pieces of paper he was holding, said he had been "brainwashed" by anti-communist propaganda and "extreme religious education".

Lim has led many aid missions to the impoverished North involving work with orphanages and food plants, according to other missionaries.

Foreigners detained by the North Korean authorities are habitually required to make public, officially-scripted pronouncements of their guilt in order to help secure their eventual release.