International pressure is mounting on Syria's president, with key European governments and the United Nations denouncing a deadly crackdown which has failed to dampen a popular uprising.
In the latest violence, security forces killed a student during a protest at Damascus University in the capital, bringing the death toll to well over 170 after more than three weeks of unrest, activists said.
There were conflicting reports about whether the student was shot or beaten to death.
The UK Government issued new advice to Britons, who were told they should not travel to Syria unless it is absolutely necessary. And the UK was among a host of nations - including the United States, France and Germany - calling for an immediate end to the bloodshed. "Reform and repression are incompatible," the French Foreign Ministry said.
The strong criticism marks a turning point because many major powers have so far held back on condemning President Bashar Assad outright, instead casting him as a reformer who has been constrained by members of his late father's old guard.
US secretary of state Hillary Clinton said late last month that Assad was a "different leader" than Libya's Muammar Gaddafi, and that many members of Congress who have visited the country "believe he's a reformer".
But with the mounting casualties, the criticism has grown. "We're aware of continuing protests on a massive scale or a large scale," said US State Department spokesman Mark Toner. He called on the government to lift restrictions on the media and "to refrain from any further violence against peaceful protesters."
Protests erupted in Syria more than three weeks ago and have been growing steadily, with tens of thousands of people calling for sweeping reforms in one of the most authoritarian regimes in the Middle East. The Assad family has kept an iron grip on power for 40 years, in part by crushing dissent.
The unrest could have repercussions well beyond Syria's borders, given the country's role as Iran's top Arab ally and a main backer of the militant Hezbollah and Hamas movements.
United Nations secretary general Ban Ki-moon personally called Assad to say he was "greatly disturbed" by the reports of violence.