|Protesters have been calling for the ouster of President Saleh since February [Reuters]
Yemen's president Ali Abdullah Saleh is in Riyadh for medical treatment, after he was injured in an attack on his compound on Friday, the Saudi royal court said in a statement.
"The Yemeni president has arrived along with officials and citizens who had received different injuries for treatment in Saudi Arabia," the royal court said on Sunday.
Friday's rocket attack on Saleh's presidential palace in the capital Sanaa marked a major escalation in the four-month-long uprising against his 33-year rule.
Pro-democracy protesters in Yemen celebrated on Sunday following news of the president's departure.
"Today, Yemen is newborn," sang dozens of youths in Sanaa's University Square, dubbed "Change Square", which has been the epicentre of anti-government protests that have raged since February.
"This is it, the regime has fallen," others chanted.
Al Jazeera has learned that Saleh arrived at King Khalid Air Base in Riyadh and was transferred to a military hospital.
The embattled leader suffered "burns and scratches to the face and chest," an official said, after the ruling General People's Congress said he was "lightly wounded in the back of the head".
Meanwhile, sources told Al Jazeera that vice-president Abd-Rabbu Mansour Hadi had taken over as acting president and supreme commander of the armed forces.
The White House later confirmed to Al Jazeera that an aide in the administration of US president Barack Obama had spoken to Hadi - though details of their conversation were not known.
The extent of Saleh's injuries has been a matter of intense speculation. When the rocket struck the mosque in his presidential compound and splintered the pulpit, he was surrounded by senior government officials and bodyguards.
Eleven guards died, and five officials standing nearby were seriously wounded.
The president delivered an audio address afterwards, his voice laboured, with only an old photo shown.
In his address, delivered on state television late on Friday, Saleh said the attack was carried out by an "outlaw gang", referring to the Hashed tribal federation led by Sadiq al-Ahmar, a powerful dissident tribesman.
Al-Ahmar's fighters have been battling government forces in the capital since a truce crumbled on Tuesday.
Witnesses said sporadic shelling and rocketfire on Saturday rattled the al-Hasaba district of northern Sanaa where al-Ahmar has his base, forcing residents to flee. The area is suffering from water and electricity cuts.
But al-Ahmar's office denied responsibility and instead blamed Saleh for the attack, calling it part of his effort to help justify a government escalation of street fighting in the capital.
Ten people were killed and 35 others injured in southern Sanaa on Friday as Yemeni troops shelled the home of Hamid al-Ahmar, the brother of Sadiq al-Ahmar, Hamid's office said on Saturday.
Hamid, a prominent businessman, is a leader of Yemen's biggest opposition party, Al-Islah (reform).
On Saturday, sources said the powerful Yemeni tribal federation battling Saleh's security forces and forces loyal to him agreed to abide to a Saudi-brokered one-week truce.
The US has condemned the violence, including the attack on the Saleh's palace, and called for him to transfer power.
"We call on all sides to cease hostilities immediately and to pursue an orderly and peaceful process of transferring political power as called for in the GCC-brokered agreement," the White House said, referring to the Gulf Co-operation Council.
Yemen's parliamentary opposition on Saturday called for an "immediate" ceasefire.
The Common Forum alliance condemned what it said was the "the dangerous twist which the clashes have taken in targeting the homes of citizens, the presidential palace, and vital installations".
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The alliance of parliamentary opposition groups urged "quick action" from the international community "to save Yemen and its people from falling into [civil] war", in the statement.
Meanwhile, Germany said it had ordered the immediate closure of its embassy in Yemen "because of current developments."
"The embassy team that is still on the ground will leave the country as soon as it is possible and safe," the foreign ministry said in a statement.
Elsewhere in Yemen, officials said police and military units had withdrawn from the southern city of Taiz after a week of clashes with pro-reform demonstrators that left dozens dead.
"Looting and scenes of chaos are spreading after the withdrawal of security forces and the army from the city," the opposition leader, who asked not to be named, told the Reuters news agency.
Tareq al-Shami, a ruling party official, confirmed the government's security forces had pulled back from the city which is about 200km south of the capital.
The UN human rights chief said her office was investigating reports that as many as 50 have been killed in Taiz since Sunday.