Saudi Arabia, Kuwait and Bahrain have now recalled their ambassadors to Syria, increasing the regional isolation of President Bashar al-Assad.
The recalls by Saudi Arabia , the Arab world's Sunni Muslim heavyweight, and fellow Gulf Cooperation Council (GCC) members Kuwait and Bahrain marks a major escalation of pressure on Assad.
His regime's repression of a pro-democracy uprising has left at least 2,059 people dead, including almost 400 members of the security forces, according to the Syrian Observatory for Human Rights.
'Saudi Arabia announces the recall of its ambassador for consultations,' King Abdullah said in a statement after Syrian security forces killed more than 50 people on Sunday.
He urged Damascus to 'stop the killing machine and the bloodshed... before it is too late.'
'What is happening in Syria is not acceptable for Saudi Arabia,’ he said in a written statement read out on Al Arabiya television.
A former US government official with knowledge of the region said the Saudi king likely went public to press concerns that had been conveyed privately.
‘I think he did it on his own because the private messages were clearly being ignored,’ the former official said, speaking on condition of anonymity.
Although several Arab states have joined the West in opposing Libya's Muammar Gaddafi, most of the region's rulers have been cautious about criticising other Arab leaders during the wave of protests this year.
Saudi Arabia had maintained its silence regarding Syria despite deep antagonism over the contest for regional hegemony with Shia Iran, the Shia militia and political movement to which Saudi Arabia's allies have lost influence in Lebanon.
King Abdullah sent Saudi troops in March to help neighbouring monarchy Bahrain put down anti-government protests, and Saudi officials have criticised the decision to put Egypt's ousted leader Hosni Mubarak on trial.
Saudi Arabia has also acted as a mediator in neighbouring Yemen, and is hosting its president Ali Abdullah Saleh, who went there for medical treatment after being wounded in a bomb attack when protests against his rule turned into open conflict.
Public criticism from Kuwait and Bahrain
The Saudi decision to recall its ambassador from Damascus was swiftly followed by Kuwait and Bahrain.
'No one can accept the bloodshed in Syria... The military option must be halted,' Kuwait's Foreign Minister Sheikh Mohammad al-Sabah told reporters.
Bahrain's Foreign Minister, Sheikh Khaled bin Ahmad al-Khalifa, said today that his country would also be recalling its ambassador for 'consultations.'
In Cairo, Sheikh Ahmed al-Tayeb, the grand imam of Al-Azhar, the leading authority in Sunni Islam, called for an end to the 'tragedy' in Syria, saying 'the situation has gone too far.'
He said Syrian leaders should work immediately to end the bloodshed and to respond favourably to 'the legitimate demands of the Syrian masses.'
The Arab League yesterday made its first official statement on the unrest, urging Damascus to immediately stop the violence with Secretary General Nabil al-Arabi calling for an impartial probe into the bloodshed.
US and European leaders have already 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.
EU nations are eyeing new sanctions against individuals and businesses linked to the clampdown, EU diplomats asking not to be identified said today.
Germany has also warned that President Assad will forfeit legitimacy if his regime continues the deadly crackdown.
'If President Assad maintains his refusal to engage in dialogue with the Syrian people and continues to resort to violence, the German government will consider he has forfeited his legitimacy in further overseeing the fate of his country,' deputy government spokesman Christoph Steegmans told reporters.
The Assad regime has pledged reform and blamed 'armed terrorist gangs' for the almost five-month-long unrest.
The crackdown has become one of the most violent episodes in the wave of unrest sweeping through the Arab world this year.
Yesterday, activists said Syrian troops with tanks had launched an assault on the city of Deir al-Zor in the east of the country, killing dozens.
The past week has seen scores of people killed in a siege of Hama, a city where Mr Assad's father launched a crackdown nearly 30 years ago, killing thousands.
