An Ontario man who travelled overseas with two friends suspected of terrorist ties is now serving time in a prison in Mauritania, a human rights group has confirmed.

Aaron Yoon, of London, Ont., is currently serving a two-year jail sentence for alleged ties to al Qaeda, Amnesty International confirmed.

Yoon, has been identified as a friend of Ali Medlej, 24, and Xristos Katsiroubas, 22. The pair, now suspected militants, died in an al Qaeda-linked siege on a gas facility in Algeria in January.

Gaetan Mootoo, a West Africa researcher with Amnesty International, told CTV News he visited Yoon in the prison on several occasions in June and July 2012.

Mootoo said the young man refused help from the organization, which conducts advocacy work on behalf of detainees imprisoned around the world.

“He fully understood Amnesty’s work and how we campaign, when I explained that to him, but still he was adamant,” Mootoo told CTV News Channel Saturday. “He didn’t want the organization to campaign on his case.”

Mootoo declined to elaborate on the nature of their discussions, as Yoon requested that their conversations be kept confidential.

Sources told CTV News that Yoon travelled to Morocco with Medlej, Katsiroubas and another unidentified man last year.

Yoon has not been linked to the gas plant attack, as he was already in prison in Mauritania when the siege unfolded.

But Medlej and Katsiroubas -- who is believed to have converted to Islam -- were among those killed in the bloody attack on the Algerian gas plant that left at least 38 hostages and 29 militants dead.

The four-day siege began Jan. 16 when al Qaeda-linked militants ambushed the plant, and ended when Algerian forces stormed the compound later that month.Authorities are investigating how Medlej and Katsiroubas were connected with the Algerian terror cell involved in the attack.

Mootoo said he was surprised by Yoon’s refusal of aid when he met with him, but said he has encountered other detainees who decline help for fear of reprisal.

Mootoo said detainees at the prison where Yoon is being held are given meals every day, and they are free to do their prayers. There is limited space for physical activity, such as walking. He said minors (those under 18) are imprisoned there, as well as many people accused of belonging to “illegal organizations.”

Canada’s Foreign Affairs department said in a statement that it is aware of Yoon’s situation overseas, and Canadian officials are providing assistance.“This assistance should not be construed as a belief of his guilt or innocence,” the department said.

Bernard Colas, Mauritania’s honorary consul in Canada, said Yoon has access to a lawyer and is being cared for. “He’s in good health, he’s well-fed, and I’m not saying that he’s happy, but he’s very well treated,” Colas said.

As Yoon remains imprisoned, a friend of the London men tells CTV News he was interviewed last summer by authorities, shortly after Yoon’s arrest overseas.

The man, whom CTV agreed not to identify, said a security official came to his door last summer to inquire about Medlej, Katsiroubas and Yoon.

“She said that they’re in trouble, we need to get some information from you,” the man said.

He had little to offer, as he did not know that the trio was overseas.

The man said Yoon and Katsiroubas mostly worshipped at the Muslim Youth Association of London, also known as the Islamic Library, he said.

People interviewed outside the London, Ont., mosque said they did not know Medlej, Yoon or Katsiroubas.

The Yoon family isn’t speaking to media, and the Medlej family appears to have left the city, CTV London reported.

RCMP has said they are looking for assistance in tracking down the people who may have helped the London men leave the country.

The identity of a fourth man who is believed to have travelled overseas with the men remains unknown.

With reports from CTV’s Todd Battis and CTV London’s Cristina Howorun