Saudi Arabia and Kuwait have recalled their ambassadors from Damascus in response to Syria's use of force to crush protests.
President Bashar al-Assad extended a tank onslaught in Syria's Sunni Muslim tribal heartland today in an escalating crackdown on protesters.
The violence has prompted an extraordinary rebuke from the Saudi king, who warned the Syrian leader to adopt reforms or risk defeat.
King Abdullah, an absolute ruler, broke Arab silence after the bloodiest week of the almost five-month uprising for more political freedoms in Syria, demanding an end to the bloodshed and recalling the Saudi ambassador from Damascus.
It was the sharpest criticism the oil giant has directed against any fellow Arab state since a tide of pro-democracy unrest began to sweep across the Middle East in January, toppling autocrats in Tunisia and Egypt, kindling civil war in Libya and rattling entrenched elites throughout the region.
"What is happening in Syria is not acceptable for Saudi Arabia," King Abdullah said in a written statement read out on Al Arabiya satellite television.
"Syria should think wisely before it's too late and issue and enact reforms that are not merely promises but actual reforms," he said. "Either it chooses wisdom on its own or it will be pulled down into the depths of turmoil and loss."
His statement followed similar messages since Saturday from the Arab League and the Gulf Cooperation Council (GCC).
Kuwait has also recalled its ambassador to Syria. Foreign minister Sheikh Mohammed al-Salem al-Sabah said Gulf foreign ministers would meet soon to discuss the situation in Syria. "Our ambassador to Syria has been summoned for consultation," he told reporters in parliament.
In Washington, a US State Department official said the Saudi king's statement was a strong signal to Syria's president. "This is another clear sign that the international community, including Syria's neighbours, are repulsed by the brutal actions of the Syrian government and will continue to stand with the people of Syria," the official said.
Meanwhile, Syrian tanks and troops poured into the eastern Sunni city of Deir al-Zor in the latest stage of a campaign to crush centres of protest against 41 years of rule by the Assad family and domination by his Alawite minority community.
"Armoured vehicles are shelling the al-Hawiqa district heavily with their ... guns. Private hospitals are closed and people are afraid to send the wounded to state facilities because they are infested with secret police," said Mohammad, a resident.
He said the al-Joura neighbourhood of Deir al-Zor, which straddles the Euphrates River, was also hit hard by government forces and thousands of residents of both districts had fled.
At least 65 people had been killed since tanks and armoured vehicles barrelled into the provincial capital, 400km northeast of Damascus, yesterday, he added.
The assault on the city, in an oil-producing province bordering Iraq, took place a week after tanks stormed Hama, where residents say scores have been killed.
With Arab leaders strikingly mum and an international response limited to verbal condemnation and sanctions on Syria's ruling hierarchy, Dr Assad had faced few obstacles in stretching the military campaign against disaffected cities and towns into the fasting month of Ramadan, until the Saudi king intervened.
Relations between Sunni Saudi Arabia and Syria's Alawite elite have been tense since the assassination in 2005 of Rafik al-Hariri, a Western-backed Lebanese Sunni statesman who also had Saudi nationality.
Riyadh backs Hariri's son Saad while Assad, along with Iran's clerical rulers, support the armed Lebanese Shia Muslim group Hizbullah. The Alawite sect is an offshoot of Shia Islam. Most Syrians are Sunnis.
Dr Assad's government says it is fighting against criminals and armed extremists who have provoked violence by attacking its troops. Activists and Western countries say Dr Assad's forces have attacked peaceful protesters.
Earlier yesterday, the Arab League, in a rare response to the escalating bloodshed in Syria, called on authorities there to stop acts of violence against civilians.
Although several Arab states have joined the West in opposing Libya's Muammar Gadafy, most of the region's rulers have been cautious about criticising other Arab leaders during the wave of protests this year.
The other regional heavyweight, Turkey, whose foreign minister is due in Damascus tomorrow, has been voicing its disapproval for months.
US secretary of state Hillary Clinton discussed the ongoing violence and security operations in Syria in a phone call with Turkish foreign minister Ahmet Davutoglu yesterday, the State Department said.
Reuters