Dozens of people were killed across Syria on Friday as protesters took to the streets to call for a "people's liberation war" and regime forces recaptured a town, a rights watchdog and activists said.
Regime forces seized the northwestern town of Khan Sheikhun in Idlib province from rebel fighters on Thursday night, activists said.
After a 10-day escalation of regime shelling of the besieged town, "it is now full of shabiha (pro-regime militiamen) and troops," an Idlib-based activist told AFP.
Syria's state news agency SANA said: "The authorities, in response to calls from citizens, chased the armed terrorist groups out of the city and surrounding farms and raided their dens."
The Britain-based Syrian Observatory for Human Rights said at least 53 people were killed on Friday -- 35 civilians, 14 soldiers and four rebels.
The watchdog reported demonstrations in several provinces across Syria, including in the capital Damascus and the northern city of Aleppo, the country's commercial hub.
Protesters braved live fire by regime forces in several areas of Damascus province, the Observatory said, while thousands more took to the streets in Aleppo, according to an anti-regime activist in the city.
"Regime forces opened fire on protesters in many of these demonstrations," the activist told AFP via Skype.
He said at least 20 people were wounded by gunfire. "Protesters called for foreign military intervention in Syria and for the arming of the (rebel) Free Syrian Army (FSA)," he said.
"We want freedom, whatever you say, O Assad!" cried the demonstrators, in amateur video posted on YouTube.
Protests were also staged in Qusayr, an AFP correspondent said in the rebel-held town of central Syria that has been under regime bombardment for months.
He said about 300 demonstrators were out on the streets after the main weekly Friday prayers.
"I lost my son 10 days ago. Many of you have lost relatives and friends in the bombing. Because of their sacrifices, it is worth continuing to fight against the murderous regime that rules us," said Dr Saleh Mahmud Sadir of Qusayr hospital.
"Every day I treat your families, and while they die the world looks the other way. Why doesn't anyone help us? Why does the world let them continue to massacre us? How long will this last?" he asked.
In the eastern city of Deir Ezzor, protests broke out in areas under army bombardment. In the province of the same name, much of which is rebel-held, eight air defence troops deserted to join the uprising, the Observatory said.
Their defections came as a top Syrian general, Manaf Tlass, a figure close to President Bashar al-Assad, was reported to have deserted the regime.
The latest bloodshed came as anti-regime activists urged a day of protests to call for a "people's liberation war," according to the Syrian Revolution Coordinators' Union.
The Observatory estimates that more than 16,500 people have been killed since the anti-Assad uprising erupted in mid-March 2011.