By Tamara Qiblawi and Hamdi Alkhshali, CNN

(CNN) -- Lebanese Prime Minister Saad Hariri is being "held captive" in Saudi Arabia in violation of diplomatic protocol, Lebanon's President said Wednesday.

Hariri quit his post earlier this month in a televised statement from the Saudi capital of Riyadh, but Lebanese President Michel Aoun said he would not recognize Hariri's resignation until he returned to Lebanon.

"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," Aoun said Wednesday, according to Lebanon's National News Agency (NNA).

"It is not possible for us to make a decision about this resignation from abroad. (Hariri) should return to Lebanon and submit his resignation so that we may refer to it and probe its reasons and ways to solve it," Aoun said, according to NNA.

Shortly after Aoun's remarks, Hariri tweeted that he was "very, very well" and that he would return to "the beloved Lebanon."

"I want to reiterate that I am very, very well and I will return if God wills it to the beloved Lebanon just as I promised. You'll see," Hariri tweeted.

On Tuesday Hariri tweeted that he hoped to return "in the next two days."

Hariri resigned in an address from Riyadh on November 4, saying his life was in danger. He has not been back to Lebanon since, fueling speculation that he is being held against his will.

A high-level ministerial source told CNN last week that Hariri's closest allies "have no idea what's going on," and that members of his own political party believe Saudi Arabia is "restricting" his movements.

His announcement plunged Lebanon into a political crisis and stoked fears of conflict between the Saudi-backed faction of the country's government and the Iranian-backed Shia militant group Hezbollah, with whom Hariri shares power.

So far Lebanon's rival political factions have called for calm, and made public statements asking for Hariri's return.

France called Tuesday for Hariri be allowed to "return home freely" and urged all sides to ratchet down tensions.

In an address to the French National Assembly, French Prime Minister Edouard Philippe said: "The goal is for Saad Hariri to be able to return home freely to clarify his situation in accordance with the Lebanese constitution. It's also important that all Lebanese parties agree to respect civil peace."