Syrian forces have swept through a north-western border region on Sunday to stem an exodus of refugees to Turkey and reportedly attacking anyone who helps them.
The latest assault followed the biggest protests across Syria on Friday in four months of anti-government unrest, despite a brutal government clampdown.
Human rights campaigners say security forces shot dead up to 19 protesters, Reuters reports.
Authorities blame the violence on armed groups and Islamists, backed by foreign powers.
Syria has barred most international journalists, making it difficult to verify accounts from activists and officials.
The number of refugees who have crossed into Turkey from Syria has reached 10,114, and another 10,000 are sheltering by the border just inside Syria, according to Turkish officials.