ANTAKYA, Turkey — Thaer Abboud volunteered to join the rebels fighting to overthrow Syrian President Bashar Assad but got a rude rejection because of his religion.
"I wanted to join a fighting group, and one rebel said, 'We don't need Alawi pigs with us.' In my head, I said, 'To hell with this. This is not a revolution.'"
Mr. Abboud, a 36-year-old resident of Latakia in western Syria, is an Alawite, a minority Muslim sect that has ruled Syria for more than 40 years but now faces a reversal of fortunes if Mr. Assad and his Alawite regime are overthrown.
Fears of religious strife between Alawites and the majority Sunni Muslim population are growing on both sides of the Syrian-Turkish border, as Syrian troops continue pounding rebels in Syria's economic hub of Aleppo.
Members of the Alawite sect are Muslims who follow an offshoot of Shiite Islam. The split between Shiite and Sunni Islam has its origins in a dispute over the leadership of the growing Islamic empire after the death of the Prophet Muhammad in the seventh century.
Alawites in Syria are estimated to make up no more than 15 percent of the population of 22.5 million.
They came to power when Mr. Assad's father, Hafez Assad, seized control in 1970. He led the country until his death in 2000 and allowed members of the sect to climb up the ranks of the military and ensured their integration into the Syrian population through business, the secret service and the army.
Fight and flight
"As the conflict has intensified and the struggle has become more sectarian-driven, the Alawites have become extremely anxious about their future in any kind of post-Assad Syria," said Fawaz Gerges, director of the Middle East Center at the London School of Economics.
"The opposition accuses Alawites of being fully in support of the Assad regime, and many of the slogans — in particular the armed wing of the opposition — have targeted Alawites because they have been seen to be the spearhead of the Assad regime."
Meanwhile, fighting continued in Aleppo on Tuesday with regime troops shelling neighborhoods across the city, including Salahhedine and Seif al-Dawla where rebels are thought to be operating. Members of the opposition reported that rebels seized police stations in two central districts.
The United Nations estimated that 200,000 people fled Syria's largest city since fighting broke out July 21 and said many went north toward the border with Turkey some 40 miles away.
Turkish authorities have provided tents and temporary housing for more than 40,000 Syrian refugees, according to the Turkish prime minister's office, while the country has remained a base for rebels.
'Alawites to the grave'
Turkish Alawites fear brutal retribution against Syrian Alawites if Mr. Assad is overthrown. They also worry that Turkey could be drawn into a sectarian war across the region.
"We are convinced that if the regime implodes, there will be wide-scale massacres of the Alawi people and of Christians, too," said Sheik Ali Yeral, a Turkish Alawite religious leader in the village of Ekinci, not far from the Syrian border.
He said Syrian protesters have chanted: "Christians to Beirut. Alawites to the grave."
Opposition leaders have tried to reassure minorities that a post-Assad Syria would be democratic and religiously tolerant, but analysts are skeptical.
"The reality is that developments on the ground will determine what will happen, in particular as the armed struggle escalates," Mr. Gerges said.
"I think the worst-case scenario is if Syria turns into all-out sectarian strife whereby neighbor turns against neighbor and village against village," he said. "This is the nightmare scenario."
Others see signs that the rebels are becoming Islamist.
"The revolution is becoming an Islamic one," said Mr. Abboud, who insists that he firmly supports the opposition, even though the rebels rejected him.
"It's not an Alawi misconception about revenge anymore. It's what some of the rebels claim themselves. The regime always said, 'You will cry for us one day.' We laughed, but now I'm beginning to believe them."
• Louise Osborne in Berlin contributed to this report.