AMMAN (Reuters) - Syrian President Bashar al-Assad faced rare dissent within his Baath Party and signs of discontent in the army over violent repression of protesters that a rights group said on Thursday had killed 500 people.
Two hundred members of the ruling party from southern Syria resigned on Wednesday after the government sent in tanks to crush resistance in the city of Deraa, where a six-week-old uprising against Assad's authoritarian rule erupted.
Diplomats said signs were also emerging of differences within the army where the majority of troops are Sunni Muslims, but most officers belong to Assad's minority Alawite sect.
The Baath Party says it has more than a million members in Syria, making Wednesday's resignations more a symbolic than a real challenge to Assad's 11-year rule.
But along with the resignations last week of two Deraa parliamentarians, they would have been unthinkable before nationwide pro-democracy demonstrations flared last month.
Syria's banned Muslim Brotherhood called on Syrians to take to the streets to demand freedom ahead of the main Friday prayers, while the Interior Ministry said citizens must not demonstrate without a licence in order to protect "the security stability of the homeland."
In a declaration sent to Reuters, the Brotherhood said: "Do not let the regime besiege your compatriots. Chant with one voice for freedom and dignity. Do not allow the tyrant to enslave you. God is great."
It was the first time that the Brotherhood, whose leadership is in exile, had called directly for demonstrations in Syria since pro-democracy demonstrations against Assad's autocratic rule erupted six weeks ago.
Criticism of Assad has intensified since 100 people were killed in protests last week and tanks rolled into Deraa. The United States says it is considering tightening sanctions and European governments will discuss Syria on Friday.
Australian Foreign Minister Kevin Rudd called on Thursday for international sanctions on Syria over the crackdown and said the United Nations should send a special envoy to investigate the killings.
But a European push for the U.N. Security Council to condemn the crackdown was blocked by Russia, China and Lebanon. China said on Thursday that Damascus should resolve its problems through talks, while Russia said Syrian authorities should bring to justice those responsible for the killings.
One diplomat said soldiers had confronted secret police at least once this month to stop them shooting at protesters.
"No one is saying that Assad is about to lose control of the army, but once you start using the army to slaughter your own people, it is a sign of weakness," he said.
"The largest funerals in Syria so far have been for soldiers who have refused to obey orders to shoot protesters and were summarily executed on the spot," another diplomat said.
The upheaval could have major regional repercussions since Syria straddles the fault lines of the Middle East conflict.
Assad has bolstered an anti-Israel alliance with Shi'ite Iran and both countries back the Hezbollah and Hamas militant groups, although Syria still seeks peace with the Jewish state.
CLASH NEAR LEBANON BORDER
Syria has blamed armed Islamist groups for the killings and accused politicians in neighbouring Lebanon of fomenting violence, allegations they have denied.
Around 1,500 Syrian women and children crossed into northern Lebanon on Thursday, witnesses said, fleeing gunfire in the Syrian border town of Tel Kelakh. It was not clear how many people were hurt in the clash but Lebanese security sources said the army had stepped up patrols in the area.
Assad sent the ultra-loyal Fourth Mechanised Division, commanded by his brother Maher, into Deraa on Monday.
Reports from opposition figures and Deraa residents, which could not be confirmed, said that several soldiers from another unit had refused to fire on civilians.
The official state news agency denied the reports.
Gunfire was heard in Deraa on Wednesday night. Water, electricity and communications remained cut and essential supplies were running low, residents said.
Rights campaigners reported shooting and arrests on Thursday in Zabadani, about 35 km (20 miles) southwest of Damascus.
The Syrian rights group Sawasiah said the death toll in six weeks of protests had risen to at least 500.
"We call on civilised governments to take action to stop the bloodbath in Syria and to rein in the Syrian regime and halt its murders, torture, sieges and arrests. We have the names of at least 500 confirmed killed," Sawasiah said in a statement. "The shelling of Deraa is a crime against humanity."
Turkey's intelligence chief met Assad on Thursday as part of a delegation sent to Damascus to suggest reforms to help end the uprising. Assad lifted Syria's 48-year state of emergency a week ago, but opposition figures said the death of 100 people in protests the next day made a mockery of his move.
Syria has been dominated by the Assad family since Bashar's father, the late President Hafez al-Assad, took power in a 1970 coup. The younger Assad kept intact the autocratic political system he inherited in 2000 while the family expanded its control over the country's struggling economy.
Assad's decision to storm Deraa echoed his father's 1982 attack on the city of Hama to crush a revolt led by the Muslim Brotherhood, killing anywhere between 10,000 and 30,000 people.
(Additional reporting by Suleiman al-Khalidi, Writing by Dominic Evans, Editing by Jon Boyle)