Justin Trudeau may have made his first high-profile, international enemy.

Canada's prime minister has drawn the ire of North Korea over his response to the life sentence of hard labour handed out to South Korean-born Canadian pastor Hyeon Soo Lim last week.

The country's state broadcaster, Korean Central News Agency, quoted a foreign ministry spokesman as saying that Trudeau has been "rashly unleashing malicious slander" following the ruling.

"We cannot suppress outrage that the Canadian government dares to pick a quarrel with our fair and just judicial decision, speaking of 'concern' and 'violation of international law' when its citizen has committed a vicious crime against us," quoted the report.

Rev. Lim, who pastors the Light Korean Presbyterian Church in Toronto, was given the sentence for allegedly attempting to overthrow the government, following a 90-minute trial before North Korea's Supreme Court on Wednesday.

He originally travelled to the communist country in January as part of a humanitarian mission and has been in detention since February.

Lim, who is in his early 60s, has made over 100 trips to North Korea since 1997, setting up nursing homes and orphanages.

After the court's decision, Trudeau told reporters that the government needs to ensure that Canadians around the world, including North Korea, are being "properly treated."

"The issues of North Korea's governance and judicial system are well known," he said.

"We are very concerned about someone being sentenced to life."

Canadian officials were able to meet with Lim over the weekend, and said they're working to get him back home.

Questions also remain surrounding the pastor's confession.

In July, Lim admitted to plotting to overthrow the North Korean regime at a news conference organized by state authorities in Pyongyang.

Other foreigners who were detained in the country and later released have said that they were coerced into making similar statements, and confessed their crimes while they were detained.

Members of his church in Toronto doubt he would threaten his humanitarian work by plotting against the state.

"We don’t see him proselytizing or offending the government in such a way to jeopardize two decades of work,” said Lisa Pak, a spokesperson for the family and the Light Korean Presbyterian Church.

The congregation is preparing for Christmas celebrations, but North Korea's statements have them on edge.

"We want to be very careful … we don't want to offend them … we just want to help them and love them," said Pak.

Amnesty International expects that Canada will have to ask other governments who have better relations with North Korea for help.

"Canada will not have all that much influence with the government in North Korea. We don't have a close relationship," said Alex Neve, secretary general of the organization's Canadian wing.

Even if that happens, securing Lim's release will likely take months and could require another public declaration of guilt

"There would have to be another public expression of regret -- a confession that he is guilty of (the crime)," said Bruce Klingner, the CIA's former deputy division chief for Korea.

"There would likely (also) have to be behind-the-scenes activity by Canadian diplomats."

North Korea is also demanding an apology from the Canadian government.