More than 200 members have quit Syria's ruling Baath party to protest at President Bashar Assad's brutal crackdown on opponents, a human rights activist says.
The resignations came in the southern province at the centre of the uprising against the regime.
Mustafa Osso said another 30 resigned in the coastal city of Banias. Most were lower-rank members.
Even though they are still small in scope - the Baath party counts more than a million members in Syria - such walkouts were unimaginable before the uprising began.
Syria's uprising against Assad's authoritarian regime started in the southern city of Daraa, the provincial capital, on March 15.
Assad has tried to crush the revolt - the gravest challenge to his family's 40-year ruling dynasty.
More than 450 people have been killed across Syria in the crackdown, with 120 dead over the weekend.
The head of the Syrian Observatory for Human Rights, Rami Abdul-Rahman, said today the latest updated death toll his group had was 454.
He said they have names of 68 soldiers who also died in the violence, raising the total to over 500.
He also said that since Wednesday, security forces carrying lists of wanted people have detained dozens around the country.
Daraa resident Abdullah Abazeid said military operations were continuing in the city today, with troops using heavy machine guns.
He added that snipers shot dead more people and that 42 have died since the military descended on Daraa on Monday.
Abazeid said the latest deaths include six-year-old girl Majd Rifai, hit by a sniper on the roof of her parents' apartment. He added that pro-government gunmen known as shabiha damaged a large numbers of shops in the city.
He said the city was still without telephones, electricity and water and lacked food and children's milk formula. Abazeid said some parents were giving their infants water and sugar for lack of powder milk.
Also today, nine Syrian human rights groups said authorities detained Rasim Atassi, senior member of the Arab organisation for Human Rights.
Syria has banned nearly all foreign media and restricted access to trouble spots since the uprising began, making it almost impossible to verify the dramatic events shaking the regime.
Two residents in Daraa said that at least five army officers had sided with demonstrators, and conscripted soldiers sent into the city were quietly refusing orders to detain people at checkpoints and were allowing some people through to get scarce supplies.
But the Syrian government denied that there had been any splits in the military, which is seen as fiercely loyal to Assad. The army also denied any defections.
Assad has blamed most of the unrest on a "foreign conspiracy" and armed thugs, not true reform-seekers.
Eyewitness accounts coming out of Syria have caused world leaders to increase their criticism of the Assad regime.
The governments of five European nations summoned Syrian ambassadors on Wednesday in a co-ordinated demand that Assad stop shooting at his people.
Germany said sanctions were possible if the crackdown did not ease, echoing remarks by Britain's foreign secretary a day earlier.
The UN Security Council failed to agree on a statement circulated by Britain, France, Germany and Portugal condemning the violence in Syria.
During consultations, several members - including Lebanon - indicated they were opposed, council diplomats said.
US officials have said Washington has begun drawing up targeted sanctions against Assad, his family and his inner circle.
Six tanks rolled into the northern port of Latakia - a key city in the heartland of Syria's ruling elite - and security forces opened fire on anti-government demonstrators wounding four, witnesses said.
Unrest in Latakia is significant because the province has strong historical ties to Assad's minority Alawite sect, an offshoot of Shiite Islam.
At least 14 people died in clashes in the city during the earlier days of the uprising.
In the Damascus suburb of Douma, security forces strengthened their control, fortifying checkpoints on roads into the area and setting up sand barriers, a resident said.
Troops were using heavy machine guns in an operation in Daraa today, said resident Abdullah Abazeid. He added that snipers killed more people and that 43 have died since the military descended on Daraa on Monday.