A Canadian who says he was tortured while detained in a Bahrain prison fears he will die in custody when he returns there this week to begin serving a five-year sentence.

"To be honest it means death," Naser al-Raas said in an interview with CBC Radio's The Current from Bahrain. "I cannot survive this conditions. No. No way."

Al-Raas said he expects to be tortured again and will also be deprived of medication he needs for a heart and lung condition.

Canadian Naser al-Raas is set to begin serving a five-year sentence this week in a Bahrain prison. (Family photo)

"I'm just afraid of going the same [route] again. The same torturing process that I was in. And nothing is sure in the future."

Al-Raas has already spent 31 days in a Bahrain prison. Upon his release, he was tried and found guilty for participating in anti-government demonstrations and sentenced to five years in prison.

He has been ordered to turn himself in to Bahrain authorities by the end of the week to begin the sentence.

Al-Raas has denied he was involved in the protests, and says he was just observing the situation.

Al-Raas, 28, lived in Ottawa from 1996 to 2000, where his mother and brother still live, according to the Toronto Star. He had been living and working in Kuwait but went to Bahrain in April to visit his sisters and fiancée.

He said he was arrested when he was about to board a plane to return to Kuwait at the Bahrain International Airport. His passport was confiscated and he was taken to Al Qala prison.

He said he was taken underground for a month and that no one, including his family or the Canadian government, knew about his whereabouts.

"First 11 days were the worst days of my life actually. [They] hit me a with rubber hose and wooden sticks. They tied me to a chair, they started to beat me and sometimes they electrified me," he said.

He said he was taken to the hospital four times while in prison.

"They were torturing me and everyone else for satisfaction. Not for getting information."

A few hours before his release, he said he was forced to sign a confession. He was later convicted in a civil court of gathering and spreading false news.

He said Canadian government officials observed his trial but have not done enough to help him.