Syrian tanks and elite troops have been heading to a northern area ahead of a possible attack on a town where soldiers reportedly joined an anti-government uprising.
The move raised the prospect of another bout of bloodshed in the nationwide crackdown on the revolt against President Bashar Assad. Despite the heavy show of government force, the reported mutiny among some units indicated cracks in the autocratic regime.
Mustafa Osso, a human rights worker who is inside Syria, said witnesses told him that thousands of troops were on the move toward the province of Idlib, near the Turkish border, in one of the biggest military deployments since the 11-week uprising began.
He said many of the troops were from the army's 4th Division, which is commanded by Assad's younger brother, Maher. Mr Osso said they were converging on Idlib from Damascus and its suburbs, the central province of Homs and the northern province of Aleppo.
"The number of soldiers is in the thousands," he said. He predicted an imminent assault and speculated that the government considers the operation to be a "decisive battle."
Al-Watan, a pro-government newspaper in Syria, said the Syrian army was launching a "very delicate" operation designed to avoid casualties in Jisr al-Shughour, a town in Idlib where witnesses and activists reported a mutiny of Syrian soldiers and loss of government control this week.
Al-Watan said some people were being held captive by armed groups that control some areas in Jisr al-Shughour and a large area of Idlib. It said gunmen had set up boobytraps and ambushes in small villages to thwart security reinforcements, and were also sheltering in forests and caves.
Activists had reported fighting in Jisr al-Shughour between loyalist troops and defectors who opposed the crackdown on protesters seeking Assad's removal.
The government said 120 members of the security forces were killed. Activists say more than 1,300 Syrians, most of them civilian protesters, have died since the start of the nationwide uprising.