Yemen's President Ali Abdullah Saleh is being treated at a military hospital in Saudi Arabia for wounds he suffered in an attack on his presidential compound on Friday.
Mr Saleh walked-off the plane when it arrived in Riyadh but the injuries to his neck, head and face were visible.
An uprising demanding that Mr Saleh leave power has led to violence bringing Yemen close to civil war.
The BBC reports that his departure leaves him in a much weakened position.
Yemen's acting president, previously the vice-president, Abd-Rabbu Mansour Hadi, has taken over, including command of the armed forces and security services.
The President's close family members travelled with him to Saudi Arabia, but his son, Ahmad, and nephews, Ammar and Yehia, are reported to be still in the country.
The departure of the President has prompted celebrations in Sanaa.
Thousands of people came out on the streets chanting and waving flags and banners.
But explosions and gun-fire has also been heard, with reports of renewed fighting between the Yemeni military and fighters of Ali Abdullah's rival al-Ahmar tribe.
At least two people were reported killed and many injured in an explosion at a facility used by a general who backs the opposition groups.
Mr Saleh was wounded during a rocket attack on the presidential compound on Friday in the capital Sanaa.
The prime minister, two deputy prime ministers and the speakers of both parliamentary chambers are already in Riyadh for treatment for their injuries.
The president broadcast an audio message on Friday, but has not appeared in public.
