And in Damascus security forces on Monday arrested pro-reform writer and journalist Fayez Sara a day after detaining two other opposition figures, the head of a rights group said.
"Students rallied in solidarity with the victims of Daraa and Banias, chanting 'We will sacrifice our soul and blood for you martyrs'," a rights activist told AFP.
The southern town of Daraa is a protest hub where rights groups say 26 people were killed on Friday while a bloody weekend crackdown left four dead in the northern coastal town of Banias, according to witnesses.
A YouTube video of the Damascus rally showed students chanting "Allah, Freedom and Syria, only!"
Abdel Karim Rihawi, president of the Syrian League for the Defence of Human Rights, told AFP some demonstrators chanted pro-regime slogans.
"Security forces intervened and made arrests," he said.
Political unrest erupted in Syria in mid-March, but anti-government demonstrations, challenging Assad to introduce major reforms, have been largely confined to the provinces.
Troops surrounded Banias with up to 30 tanks on Monday as residents buried four civilians killed over the weekend and the town's electricity supply was cut off, witnesses, activists and residents told AFP.
"The army is shooting sporadically to provoke people, but not a single demonstrator has fired," an activist said, adding that calls were made from mosque minarets urging the army to hold fire.
The activist said three soldiers had tried to defect and join the demonstrators after refusing to fire at them, and their officers shot and wounded the three.
"Bashar al-Assad is sending us a message: punish those who dare demand freedom with death," a university professor told AFP by telephone.
Government forces on Sunday killed at least four civilians and wounded 17 in a residential area of Banias, witnesses said.
Nine soldiers, including two officers, were later killed and several wounded when their patrol was ambushed outside the town, the official SANA news agency said.
Anas al-Shuhri, a leader of the protest movement, said three civilians were "killed by sniper fire" and blamed "regime henchmen" for the violence.
He said they "had fired on the army to push them to respond" against peaceful demonstrators and accused them of "seeking to stir sectarian unrest."
Rihawi spoke of several arrests in Banias overnight, including associates of former vice president Abdel-Halim Khaddam, a dissident living in exile in Paris since 2006.
He also reported Sara's arrest. "We don't know the reasons or where he is being detained," said Rihawi of the 61-year-old member of the "Damascus Declaration" opposition group.
Sara was the third opposition figure arrested since Sunday when security services snatched communist party member Georges Sabra and Ahmad Maatouk of the also banned Socialist Democratic Union party, Rihawi said.
The National Progressive Front, a coalition of parties headed by the ruling Baath party, blamed the violence on foreign plotters.
Syria "confronts dangerous challenges stemming from the hatching of conspiracies and external pressures exerted upon it," SANA quoted a front statement as saying.
"To achieve political, economic and democratic reforms, peace and stability must prevail," it said.
Assad last month ordered a legal committee to draft new legislation to replace emergency laws, in force since 1963, which give security services great leeway to crush dissent.
France condemned deadly assaults against anti-government protesters. "Reform and repression are not compatible," a foreign ministry spokeswoman said.
Germany also slammed the "shocking" violence against peaceful demonstrators, and called on Damascus to stop "grave human rights violations."
Meanwhile the authorities freed 190 people arrested earlier this month during protests in Douma, north of Damascus, a relative of one of those released said Monday.
The source, who declined to be named, added that Assad met on Sunday with relatives of people killed in Douma and told them a probe into the bloodshed was under way. At least eight people were killed this month in Douma.
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