High ranking Canadian officials are in North Korea trying to secure the release of a pastor, imprisoned in the pariah state since 2015.

Canada's Prime Minister Justin Trudeau confirmed on Tuesday his national security and intelligence adviser Daniel Jean is in Pyongyang leading a team to discuss the case of Toronto Presbyterian pastor Hyeon Soo Lim, the Canadian Broadcasting Corporation (CBC) reported.

Detained in early 2015, Lim was sentenced to a life of hard labour on December 16, 2015 for 'harming the dignity of the supreme leader,' 'trying to use religion to destroy North Korea' and 'assisting North Koreans escape.'

Now in his 60s, Lim's health is worsening according to a Canadian delegation who visited him last year and letters to his friends say he is suffering from high blood pressure and stomach pains.

Confirming the presence of the diplomatic negotiation, Trudeau's spokesman Cameron Ahmad, said: 'Obviously, Pastor Lim's health and well-being remain of utmost importance to the government of Canada as we continue to engage on this case.'

It comes at a high of heightened tensions between North Korea and the West after US President Donald Trump reacted with fury to an intelligence report that suggested Pyongyang had the nuclear firepower to hit America.

Trump warned North Korea's supreme leader Kim Jong-un any threats would be met 'with fire and fury and, frankly, power the likes of which the world has never seen before'.

North Korea responded by saying on state media it is considering a strike on the US Pacific territory of Guam.

Pyongyang has been carrying out several missile tests in recent weeks and has tested nuclear devices five times, including two intercontinental ballistic middles (ICBM) in July, in what are perceived to be acts of aggression towards the West.

In response the UN approved further economic sanctions on North Korea on Saturday in an attempt to pressurise Kim Jong-un to give up his nuclear weapons.

A senior Canadian official said their trip was solely linked to Lim's condition and was not related to the increasing global tensions with the state.