Aaron Yoon, 24, was convicted last July on charges of having ties to a terrorist group and of posing a danger to national security and sentenced to two years.
The new request stems from Yoon's alleged connections to two other Canadians involved in a terror attack on an Algerian gas plant in January, said a judicial official, who insisted on anonymity because he was not authorized to speak to journalists.
Mauritanian prosecutors are now accusing Yoon of having acted in connivance with terrorists before the Jan. 16 attack and four-day siege that ended with the deaths of 37 hostages and 29 terrorists, the official said. Among those found dead at the scene were two Canadians who had attended his London, Ont., high school.
The three reportedly had travelled to Morocco together, though Yoon maintains he went to Mauritania for religious study. He was arrested in December 2011, and has maintained his innocence in having anything to do with the January 2013 terror attack.
"I came to Mauritania to study the Qur’an," he told the court on Monday, appearing briefly in a white traditional Mauritanian robe.
CBC News aired excerpts of an interview last month with a man it said was Yoon speaking from prison.
The man claimed he had been tortured and beaten behind bars, and denied being involved in terrorist activities.
He also told CBC he didn't know how the two Canadians killed in Algeria earlier this year had become linked with militants.
Yoon is reported to have travelled overseas with Ali Medlej and Xristos Katsiroubas, the two men whose bodies were found at the site of January's Algerian gas plant siege.
The court is due to render its verdict on June 9 as to whether Yoon must serve the longer sentence.
--With files from The Canadian Press
Also on HuffPost