Beirut, Lebanon (CNN) Lebanese Prime Minister Saad Hariri is being "held captive" in Saudi Arabia in an "act of aggression" against Lebanon, according to the country's President.

President Michel Aoun dubbed Hariri a hostage in the most strongly worded statement since the Prime Minister quit his post earlier this month from the Saudi capital of Riyadh.

"What happened wasn't the resignation of a government, but an act of aggression against Lebanon, its independence and dignity, and against relations between Saudi Arabia and Lebanon," Aoun said Wednesday, according to a statement released his office.

"We do not accept that (Hariri) remain hostage, and we do not know the reasons for his captivity."

"Nothing justifies Prime Minister Saad Hariri's not returning to the country in 12 days. We therefore consider him detained and held captive, which violates the Vienna Convention and the Universal Declaration of Human Rights."

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