Syrian security forces arrested at least 46 pro-democracy activists on Saturday, human rights groups said.
The raids come one day after the slaying of nine of their fellow protesters.
The suspected dissidents were rounded up by secret police in three cities across Syria.
Eleven people were arrested during a sit-in at a mosque in Damascus.
Officers arrested another 18 in Douma, just north of the capital, while 17 were detained in the industrial city of Homs.
Activists want President Bashar al-Assad, who inherited power from his father 11 years ago, to implement democratic reforms.
The Syrian leader has called the movement “a foreign plot” and denies his forces killed protesters during Friday’s “Day of Martyrs.”
Witnesses said security forces fired live rounds during rallies held in memory of those who have died since protests began in mid-March.
Rights groups say at least 60 people have lost their lives; the government says the figure is closer to 30.