Saudi Arabia recalled its envoy to Syria in a major escalation of international pressure Monday after security forces killed more than 50 people and the regime defended its crackdown on "outlaws."
The surprise move by Riyadh, the Middle East's Sunni Muslim heavyweight, followed condemnation by Pope Benedict XVI and the Arab League over the continuing bloodshed.
"Saudi Arabia announces the recall of its ambassador for consultations," the king said in a statement and urged Damascus to "stop the killing machine and the bloodshed... before it is too late".
"The kingdom does not accept the situation in Syria, because the developments cannot be justified," he said, urging "comprehensive and quick reforms".
"The future of Syria lies between two options: either Syria chooses willingly to resort to reason, or face being swept into deep chaos, God forbid," he said.
He branded the crackdown on protests immoral and in breach of Islamic teaching.
"Large numbers of martyrs have fallen, their blood has been shed, and many others have been wounded... This is not in accord with religion, values and morals," he said.
He reminded the Syrian government of Saudi support "in the past" but said that the Gulf kingdom had to take an "historic" decision.
The US envoy to Damascus, Robert Ford, who returned to Syria on Thursday, said in a US television interview on Sunday that Washington will "try to ratchet up the pressure" on President Bashar al-Assad's regime.
Ford, who infuriated the Syrian authorities with a visit to the flashpoint protest city of Hama last month, also told ABC news that the violence against protesters was "grotesque" and "abhorrent."
US Secretary of State Hillary Clinton meanwhile has asked Turkish Foreign Minister Ahmet Davutoglu to press Syria to "return its military to the barracks," during his visit to Damascus on Tuesday, an official said.
Clinton spoke by telephone with Davutoglu on Sunday, State Department spokesman Mark Toner said in Washington.
"Secretary Clinton discussed the US position that Syria must immediately return its military to barracks and release all prisoners of concern," Toner said.
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Activists said security forces backed by tanks killed 42 civilians in the eastern city of Deir Ezzor and at least 10 more in the central town of Hula on Sunday.
"Forty-two civilians have been killed and more than 100 wounded in Deir Ezzor by gunfire from the armed forces and security agents," Syrian League for the Defence of Human Rights head Abdel Karim Rihawi told AFP.
In Hula in Homs district, at least 10 people were killed in a military assault, Rihawi said.
"About 25 tanks and troop carriers entered Hula and carried out military operations," another activist, Rami Abdel Rahman of the Britain-based Syrian Observatory for Human Rights, said earlier.
The Observatory also reported two civilians shot dead in Idlib in the northwest by security forces firing on mourners at a funeral.
Abdel Rahman said hundreds of demonstrators took to the streets of Syria's second city Aleppo in the north late on Sunday, demanding the fall of the regime and proclaiming solidarity with Deir Ezzor and Hama.
Assad roundly defended his security forces, however.
"To deal with outlaws who cut off roads, seal towns and terrorise residents is a duty of the state which must defend security and protect the lives of civilians," state news agency SANA quoted him as saying.
SANA also quoted an official military source as dismissing claims that the army was shelling Deir Ezzor with tanks as "completely false and untrue."
The latest bloodshed came as the pope said he was "following with deep concern the dramatic and increasing episodes of violence in Syria that have led to numerous victims and grave suffering."
The Arab League made its first official statement on the unrest, calling on Damascus to "immediately" stop the violence that has raged since mid-March.
Secretary General Nabil al-Arabi also urged an "impartial probe" into the bloodshed, warning against "chaos" and "religious strife" in Syria, it said.
US and European leaders pledged to consider new steps to punish Syria after security forces killed more than 30 people on the first Friday of Ramadan, the holy Muslim month of fasting.
Syria's government has sought to crush the democracy movement with force, leaving at least 2,059 people dead, including 391 members of the security forces, according to the Syrian Observatory.
The Assad regime has pledged reform and accused "armed terrorist gangs" of fomenting the unrest.