The sons of an Iranian-Canadian university professor who died in a Tehran prison last month urged Prime Minister Justin Trudeau on Wednesday to speak out publicly and pressure the Iranian government to free their mother.

They also want Canada to seriously investigate their father's arrest and death.

Ramin and Mehran Seyed-Emami said in a joint interview with The Associated Press that they have been speaking out despite intimidation and threats. They said they believe it is their only hope for getting their mother back to Vancouver after she was stopped at the airport March 7 and barred from leaving Iran.

Their father, Kavous Seyed-Emami, a 63-year-old professor of sociology at Imam Sadeq University in Tehran and the managing director of the Persian Heritage Wildlife Foundation, died in February.

His death sparked new anger in Iran over the treatment of detainees, especially after nearly 5,000 people were arrested in the wake of nationwide protests at the start of the year.

Kavous Seyed-Emami, (right), is seen in this undated photo with his son, Mehran, and wife, Maryam. (Family photo)

Iranian authorities told the family that Seyed-Emami killed himself while in custody. But Ramin, a musician who performs under the stage name King Raam, said he and his brother "feel that the guards in the prison are responsible directly for his death."

He said he was shown video of his father in a cell, pacing around, taking off his shirt, and going into the bathroom. Then "eight hours later they come in and they bring the body out of that room, so there is no footage or film of the death or how it happened," Ramin said.

"The fact that he was unmonitored for eight hours is such a suspicious thing," Ramin added.

He complained that the family is "not being allowed to pursue a proper investigation into his death, or why he was arrested in the first place, or how he was treated the whole time."

Iran alleges espionage

Tehran prosecutor Abbas Jafari Dolatabadi alleged the professor was part of an espionage ring that collected information on "strategic areas."

The brothers vehemently defended his innocence. "There is no shred of evidence against him, nothing," Mehran said.

Mehran said his father's legacy "was one of building bridges, of uniting people."

Kavous Seyed-Emami, 63, was a professor of sociology at Imam Sadeq University in Tehran and the managing director of the Persian Heritage Wildlife Foundation. (CP/HO, Samid Lotfi, Center for Human Rights in Iran)

"He was a lover of not just Iran but its wildlife, its people," Mehran said.

Mehran said his father encouraged his sons to vote in Iran's election for moderate President Hassan Rouhani, "to vote for change, to vote for hope.

"We cannot believe the lack of support we've seen from the Iranian government," he said. "It's so unfortunate that they would do this to one of their sons."

Meeting with Freeland

Ramin and Mehran met Foreign Affairs Minister Chrystia Freeland in New York on Wednesday to urge stepped up pressure on Iran.

"She reassured us they're doing their best to get my mother home as soon as possible," Mehran said. "We are grateful for their effort but ... we need them to speak up publicly, not just privately.

"We asked for the prime minister, Mr. Trudeau, to make an official statement on behalf of the government, to pressure the Iranian government to release my mother, and to have a serious investigation into the case of my father," he said.

The brothers said leaving Iran without their mother, Maryam Mombeini, was very difficult. Ramin said she implored them to board the plane and go without her.

Thank you to the Seyed-Emami brothers for meeting today. Canada will continue to demand answers in the death of Kavous Seyed-Emami and for the Iranian authorities to allow for his widow, Maryam Mombeini, a Canadian citizen, to return home. <a href="https://t.co/M7VdgFq5Vi">pic.twitter.com/M7VdgFq5Vi</a> —@cafreeland

Intimidation in Iran

Their house in Iran was raided twice, and the Iranian Revolutionary Guards packed documents, computers, hard drives, photo albums of their childhood and other items into eight suitcases in the first raid, Ramin said.

Ramin said Iranian authorities started a campaign of intimidation after their father's arrest. He said it included constant surveillance, death threats and "a very disgusting smear campaign against our family using footage that they had stolen from our home when they raided the place.

"They put this all up on national television," he said, "and slowing down the film and putting some scary music on it and attacking my father's character."

He said that he and Mehran started to speak out anyway.

"We really believe speaking out actually ensured more safety and security for us," Ramin said. "They wanted us to stay silent and be afraid."

Ramin said his mother is now relying on family and friends for financial support because Iranian authorities seized the deeds to the family home and the other assets they had.

"We just want to have her home as soon as possible," Mehran said. "Our father lives inside of us and I am sure he is proud of us for being outspoken, for standing up for what's right, for the truth."