Lebanon’s president on Wednesday accused Saudi Arabia of holding hostage prime minister Saad al-Hariri along with his family - the first time he has explicitly said he was being held - and called this an act of aggression, Reuters reported.

“We will not accept him remaining a hostage whose reason for detention we do not know,” President Michel Aoun said in a statement.

Hariri’s abrupt resignation as premier in a statement televised from the Saudi capital Riyadh on Nov. 4 thrust Lebanon to the front of a Middle East contest for power between Saudi Arabia and Iran.

Aoun has said he will not accept Hariri’s resignation until he returns to Lebanon to formally submit it and explain his reasons, which Hariri has said he will do in the coming days. Lebanese politicians close to Hariri said last week that Saudi Arabia had coerced him into quitting.

Hariri has denied being kept in custody by Saudi Arabia and pledged on Wednesday to return soon. Riyadh denies detaining him or forcing him to resign.

Hariri wrote on Twitter that he was “perfectly fine” and would return, “God willing, to dear Lebanon as I promised”. On Wednesday he said he would return in a couple of days but that his family was staying in Saudi Arabia, calling it “their country”.