"Six months. More than ever determined to (continue) the March 15 uprising," activists wrote on Facebook page The Syrian Revolution 2011, one of the main engines of the revolt.
The planned protests follow another day of killings, with human rights activists saying security forces shot dead eight people, including a child, in a huge sweep on Wednesday against anti-regime protesters in northwestern Syria.
Armed with heavy machine guns, the forces cut off roads leading to the Jabal al-Zawiya villages of Baliun, Marayan, Ihsem, Al-Rami and Ablin, setting up checkpoints and arresting several people, said the Britain-based Syrian Observatory for Human Rights.
Four people were killed and dozens more wounded in the operation, it said, adding that 100 people were arrested including the family of Riad al-Assad, a soldier who defected.
Elsewhere, a child was killed when security forces opened fire to disperse a demonstration in the village of Janudiya near the Turkish border, while another three people were shot dead in the flashpoint central provinces Hama and Homs, the Observatory said.
Ablin is the hometown of Lieutenant Colonel Hussein Harmush, the first military officer to publicly declare his desertion in early June in protest against the repression of the protest movement.
He managed to leave Syria and had been leading the "Brigade of Free Officers," a group of dozens of officers who have deserted the regime.
But according to opposition sources in Damascus, he was recently captured in Turkey by Syrian intelligence agents and brought back to Syria.
State television meanwhile announced that it would broadcast the colonel's "confession" at 1730 GMT on Thursday.
A week ago, three other military defectors were killed in Ablin when security forces raided the home of Mohammed Harmush, the colonel's brother, the Observatory said.
Mohammed Harmush was abducted during the raid and "his body was returned to his family," said the Observatory's head, Rami Abdel Rahman.
Copyright AFP (Agence France-Presse), 2011