Saudi Arabia, Kuwait and Bahrain have recalled their ambassadors from Damascus amid mounting pressure from the Arab world against Syria's brutal crackdown on anti-government protests.
The Saudi king on Monday condemned the crackdown, and urged the Syrian government to implement political reforms.
"What is happening in Syria is not acceptable for Saudi Arabia," King Abdullah said in a written statement.
"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."
Later in the day, Kuwait and Bahrain followed Saudi Arabia, announcing they too had decided to recall their ambassadors from Damascus for "consultations".
"No one can accept the bloodshed in Syria... The military option must be halted," Sheikh Mohammad al-Sabah, Kuwait's foreign minister told reporters.
His comments came a day after the Gulf Co-operation Council urged Syria to "end the bloodshed". In addition, the Arab League, which had been silent since the uprising began, said it was "alarmed" by the situation and called for the immediate halt of all violence.
Nabil El Araby, the head of the Arab League, urged Syrian authorities to launch "serious dialogue" with protesters.
In Jordan, Foreign Minister Nasser Judeh was quoted by Jordan's official Petra News Agency on Monday describing the escalation in violence as "disturbing." He urged the government to follow through on promised reforms, but added that Amman does not interfere in Damascus' affairs.
Al Jazeera's Nisreen el-Shamayleh, reporting from the Jordan-Syria border, said: "In Jordan for the first time a Jordanian official spoke out since the unrest in Syria began.
"The relations between Syria and Jordan haven't exactly been the best within the last few years.
"There has always been tensions that have marred their relations and Jordan has tried as much as possible to shy away from commenting on what is happening in Syria to avoid any escalation with the regime."
Lebanese intellectuals and writers gather in Beruit's Martyrs' square for the "first significant protest" in solidarity with the Syrian people, Al Jazeera's Rula Amin reports from Beirut.
Turkey, which borders Syria and until recently was a close ally and a major trade partner, said it would send its foreign minister to Damascus on Tuesday to deliver a strong message against the crackdown.
Assad has brushed off months of criticism and sanctions, blaming armed gangs for the violence. But on Monday, Syrian state TV reported that he had replaced the country's defence minister, Ali Habib, with Dawoud Rajha, the army's chief of staff. The official reason for Habib's replacement is due to illness, the report said.
"The government feels it is in a race with time as the Arab pressure and international pressure is increasing," Amin said.
The chorus of condemnation came as Syrian activists reported renewed artillery fire in the eastern city of Deir ez-Zor.
The Syrian Observatory for Human Rights reported that security forces had shot dead a mother and her two children fleeing the assault.
In-depth coverage of escalating violence across Syria
"The woman and her two children were trying to flee the Huweika district for somewhere safer when they were targeted by a security patrol," the group said, citing residents.
Al Jazeera's el-Shamayleh said: "We have just been speaking to activists in Deir ez-Zor and right now as we speak several snipers are controlling the top of buildings in the heart of the city.
"We also understand that the crackdown that started at dawn on Monday continued until noon."
In Deraa, at least three people were killed and scores injured in a funeral procession, our correspondent reported on Monday.
Troops also entered Maarat an-Numan in the northern province of Idlib at dawn on Monday, according to opposition activists.
"Forces entered the city from its eastern side and they are preventing the residents from entering or leaving the city,'' the Local Co-ordination Committees said in a statement.
Some activists say more than 300 people have died in the past week, the bloodiest in the five-month uprising against Assad.
But analysts said Monday's moves from Gulf Arab states to recall their ambassadors could mark a turning point in the crackdown.
|Arab League has said it is "alarmed" by the situation in Syria and called for an end to violence [Reuters/YouTube]
Commenting on the recalling of the Saudi ambassador, Ali al-Ahmed, director of the Institute for Gulf Affairs in Washington, told Al Jazeera that the move was "a watershed moment" and "foretaste of things to come".
"The Syrian regime is really scared of losing Saudi Arabia as a friendly nation."
However, Ahmed said Saudi Arabia was "not in a position to give such advice to Syria in terms of reform".
"Saudi Arabia itself lacks these reforms and has invaded Bahrain to stop a revolution and so it does not have that legitimacy. However, Saudi believes this is the right moment to publicly intervene and give the uprising a huge boost because they now see the success of this uprising to be real, especially after the Turkish position, the GCC and Arab League statements, all of which were preludes to the Saudi position," he said.
The government's crackdown on protesters demanding political reforms and an end to the Assad family's 40-year rule has left more than 1,700 dead since March, according to activists and human rights groups.
Assad's government disputes the toll and blames a foreign conspiracy for the unrest, which at times has brought hundreds of thousands of protesters into the streets.
The regime intensified the crackdown a week ago on the eve of Ramadan, the holy month in which many Muslims fast from dawn to dusk, then eat meals and gather in mosques for nightly prayers. The government has been trying to prevent the large mosque gatherings from turning into more anti-government protests.