North Korea has released a Canadian pastor serving a life sentence for 'trying to overthrow the regime' on humanitarian grounds, Pyongyang said on Wednesday.

Hyeon Soo Lim, 61, was jailed 2015 for 'subversive acts against Pyongyang', accusations which Canadian authorities have strongly denied.

His release followed the arrival of a Canadian delegation sent to Pyongyang to discuss the case of Pastor Lim, also known as Rim Hyon Su.

Hyeon Soo Lim, pictured in 2015, has been released by the North Korean government on humanitarian grounds, described as 'sick bail' in a statement from Pyongyang

'Rim Hyon Su, a Canadian civilian, was released on sick bail according to the decision of the Central Court of the Democratic People's Republic of Korea on August 9, 2017, from the humanitarian viewpoint,' North Korea's official KCNA news agency said today.

He was released amid heightened tensions between North Korea and North America, with both North Korea's Kim Jong-Un and U.S. president Donald Trump making threats of outright nuclear war.

Pyongyang's volatile dictator warned he was 'carefully examining' plans to make 'an enveloping fire' around the US island of Guam which is home to about 163,000 people and a sprawling American military base.

It came after US President Donald Trump's apocalyptic warning that North Korea faces 'fire and fury like the world has never seen' over its nuclear programme.

America then released images of supersonic bombers flying over the Korean peninsula while American airmen in Guam have said they are ready to 'fight tonight'.

The North said the training mission 'proves that the U.S. imperialists are nuclear war maniacs'.

Pastor Lim's release followed the arrival of a Canadian delegation, including the country's national security advisor, sent to Pyongyang to discuss his case with the government

Yesterday, a Canadian government spokesman confirmed that the country's national security advisor Daniel Jean was in Pyongyang.

'A Canadian government delegation is currently in Pyongyang, DPRK, to discuss Pastor Lim's case,' Trudeau spokesman Cameron Ahmad said.

'Pastor Lim's health and well-being remain of utmost importance to the government of Canada as we continue to engage on this case,' he said.

'As this is an active case, we will not provide further comment at this time.'

Lim's family told local media they have become increasingly worried about his welfare since the death of an American student in June just days after he had been released from a North Korean prison.

Finger on the button: The release of Pastor Lim comes amid heightened tensions between North Korea and the west, in particular the United States

At the time of his arrest, other members of the close-knit circle of ethnic Korean missionaries in Canada and the United States called Lim one of the most influential Christian missionaries operating in North Korea.

He had visited the country dozens of times, working with orphanages and nursing homes.

But some projects he worked on, including a noodle plant and flour mills, were linked to associates of Jang Song-Thaek, the purged uncle of leader Kim Jong-Un. Jang Song-Thaek was arrested and executed for treason in December 2013.

Lim told CNN last year that he now spends his days in prison digging holes.

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.