"There is a Christian militia group that set up checkpoints and walk around the streets searching houses for dissidents," a woman from the Christian quarter told The Guardian.
Many Christians and Alawites back the regime of President Bashar Assad because they fear repression should Sunni Islamists gain control.
Syrian helicopters are dropping bombs the size of trash cans onto rebel forces in the commercial hub. However, because the aircraft hover at high altitudes to avoid gunfire, residents have several seconds to flee the explosives.
In other fighting, at least five people at a Palestinian refugee camp south of Damascus were killed Thursday by shelling as rebel forces clashed with government troops.
Tel Chehab, a town on the border with Jordan where refugees fled the country, was seized from rebels Thursday morning by hundreds of government troops backed by 20 tanks, the Syrian Observatory for Human Rights said.
All told, more than 300 people were killed across the country Wednesday, including 67 in Damascus and its suburbs, the Local Coordination Committees said.
The Syrian Network for Human Rights said at least 200 people were killed, including 51 in Damascus and its suburbs.
As Syrian warplanes and artillery shelled Aleppo, Egyptian President Mohammed Morsi warned Assad to step down while he still could.
"Your time won't be long," Morsi said in remarks directed at Assad during an Arab League foreign ministers conference in Cairo.
He said Assad must learn from "recent history," which has seen Tunisian, Libyan, Yemeni and Egyptian dictators overthrown in uprisings, and step down before it's too late.
"There is still a chance to stop the bloodshed," Morsi said. "Don't take the right step at the wrong time ... because that would be the wrong step."
Morsi, an Islamist and Egypt's first democratically elected president, told the Non-Aligned Movement summit in Tehran Thursday it was an "ethical duty" to support the Syrian people against the "oppressive regime" in Damascus.
Syria's top regime spokesman said Monday Morsi had become a U.S. and Israeli stooge, no different from ousted Egyptian President Hosni Mubarak.
"The beard is the only difference," Information Minister Omran al-Zoubi said in an unusual televised news conference.
Morsi's warning came as the Obama administration said Iraq has a responsibility to require Iranian planes flying to Syria through its airspace to land and be inspected to prove they're not carrying weapons for Assad regime forces.
The State Department said Wednesday Iraq had an obligation under U.N. Security Council resolutions to insist Iranian planes suspected of flying arms to Syria through Iraqi airspace land so the cargo could be inspected.
The flights, which were suspended in March, resumed in July after an explosion killed several senior Syrian regime members, The New York Times reported.
U.S. intelligence assessments indicate the flights are carrying weapons and military equipment, the State Department said.
A spokesman for Iraqi Prime Minister Nouri al-Maliki was quoted by the Times as saying Iraq first needed evidence the flights are not carrying humanitarian aid as Tehran claims.
"Until now, there was no evidence from the Americans regarding weapons," Ali al-Moussawi said.
The State Department did not immediately respond. Tehran had no immediate comment on Washington's allegations.