At least 120 people are reported to have died since Friday, when security forces opened fire on huge protests and then attacked mourners who turned out on Saturday to bury the dead.
There are now reports security forces have begun rounding up opponents in raids on homes across the country and set up checkpoints in the capital Damascus.
At least one person was shot dead yesterday in the coastal town of Jableh and several more were wounded.
Despite the crackdown, the protests show no sign of abating.
Student groups are now calling for a strike, and Western governments, including Australia, are urging their citizens inside Syria to leave immediately, saying the security environment is getting worse.
Human Rights Watch (HRW) urged the United Nations to probe the "carnage" from the massive Good Friday demonstrations and called for sanctions against officials responsible for the killings.
About 10 people were arrested on Sunday in Damascus, Homs, Daraa and other towns, activists said.
A group of more than 100 intellectuals and journalists, in a joint statement, condemned the regime's crackdown and urged state media workers to resign.
The Syrian Observatory for Human Rights said dozens of people were detained in northern Syria on Friday, just a day after president Bashar al-Assad lifted decades of emergency rule.
Tens of thousands swarmed cities and towns across Syria on Friday to test implementation of the reforms, but security forces used live rounds and tear gas against them, activists said.
