Syria ignored mounting international pressure to halt its bloody crackdown on anti-government protesters Wednesday, as small signs of cracks in the regime began to emerge with the reported resignations of numerous low-level Baath Party members.

Germany joined France, Britain and Italy in threatening sanctions unless President Bashar al-Assad’s regime stops gunning down protesters, and the U.N. Human Rights Council, based in Geneva, agreed to a U.S. request for a special session on Syria on Friday.

But members of the U.N. Security Council did not reach agreement on a statement condemning the crackdown, as an effort backed by European governments and the United States ran into resistance from China, India, Lebanon and Russia.

With Syrian authorities seemingly intent on stamping out a rapidly swelling uprising against 40 years of Assad family rule, there was little indication that the international pressure was having any effect.

The reported resignations from the ruling Baath Party were described by human rights groups and activists, who said they had heard multiple accounts from several locations around the country. Wissam Tarif, director of the human rights research group Insan, said he was trying to confirm the identities of dozens of party members who had stepped down in the coastal town of Banias, the Damascus suburb of Douma and the town of Deir al-Zour.

The southern town of Daraa, where the uprising first took root, remained under siege for a third day, and with telephone communications cut off, few reports emerged about what was happening there.

Footage broadcast on the al-Arabiya TV network from the nearby Jordanian border showed columns of smoke rising from the town, suggesting that it was still coming under artillery fire from troops attempting to suppress the protests. A resident who managed to escape into Jordan told the al-Jazeera network that bodies were lying in the streets because people did not dare go outside to retrieve them, that soldiers in the town had ransacked stores and that electricity and water were cut off.

Amateur video footage obtained by activists showed what appeared to be fresh reinforcements of troops heading into Douma, another center of the protest movement. Human rights groups say more than 450 people have been killed since the protest movement erupted in mid-March.

Details of the reports coming out of Syria could not be independently confirmed because authorities are refusing to issue visas to foreign journalists. But a report presented on Wednesday to the U.N. Security Council said that as many as 400 civilians have been killed by Syrian security forces, with more than 100 people killed between last Friday and Sunday alone.

Despite Syria’s “promise of reform,” the government crackdown has “intensified dramatically,” said B. Lynn Pascoe, the U.N. undersecretary general for political affairs.

There have been unconfirmed reports from witnesses in Daraa that some troops there refused to participate in the crackdown when tanks rolled into the town on Monday. A video posted on YouTube on Wednesday showed army soldiers seemingly forming a protective barrier alongside demonstrators as they fled gunfire from an unspecified source in the nearby town of Izra. There was no indication of when the footage was taken, and its contents could not be independently verified.

A split in the security services, presumed to be fiercely loyal to the regime, could dramatically tilt the direction of the uprising in Syria, as happened in Yemen, Egypt and Tunisia, where troops refused to open fire on protesters. Widespread defections from the ruling party could also significantly undermine the Syrian government’s claims that the protests are being carried out by Islamic extremists and “terrorists.”

Most of the reported Baath Party defectors were apparently low-ranking members of local party committees. But Tarif, the human rights activist, said any such moves would nevertheless be taken seriously by Assad’s government. “It is surprising because these are people who have been benefiting from the regime, and they are running risks,” he said.

An activist in Banias contacted by telephone confirmed that 30 local Baathists, most of them doctors, lawyers and other professionals, had approached protest organizers in the town earlier in the day to announce that they were resigning and lending their support to the opposition. Though none held positions in the government, “this puts great pressure on the regime,” said Rami Mustafa, 23, a student activist. “I think in the coming days we will see more.”

One of the purported members, who asked to be identified only as Abu Mohammed, said in a telephone call that he was among “a large number” of Baathists who had signed a statement announcing their resignations in protest of the brutality of the crackdown in Daraa.

An additional 200 party members in Daraa announced their resignation in a statement reported by Reuters. The crackdown in Daraa, which began when tanks entered the town on Monday, came after seven key local officials, including the mufti and two members of parliament, resigned from the party.

Staff writer Colum Lynch contributed to this article from the United Nations.