Syrian troops travelling on tanks, armoured personnel carriers and buses have moved into two northern towns.
They have gathered in Maarat al-Numan and Khan Sheikhoun, which sit on the road linking Damascus and Aleppo.
UN Secretary General Ban Ki-moon has urged Syria to halt the bloodshed and "stop killing people".
The UN says that at least 1,100 people have died as the government has violently sought to quash protests over the past three months.
State television said late on Thursday that President Bashar al-Assad's cousin, Rami Makhlouf, intends to give up his business interests - which span telecommunications, construction and oil - and donate his profits to charity.
"As for his businesses, they will be directed so that they [...] create jobs and support the national economy. He will not enter into any new project that (brings) him personal gain," the television said of the tycoon.
A first cousin of President Bashar al-Assad, Rami Makhlouf is arguably the most powerful economic figure in Syria.
He has been the subject of persistent accusations of corruption and cronyism, and protesters in Syria have specifically targeted his business interests.
The BBC's Jim Muir, reporting from Beirut, says that for someone like Mr Makhlouf - who is part of the elite Syrian inner circle of power - to make such a declaration, it is clearly a sign that the regime feels under mounting pressure.
Mr Makhlouf is one of a number of Syrian officials on the European Union's sanctions list, which includes asset freezes and travel bans.
President Assad is facing the gravest threat to his family's 40-year ruling dynasty, as unrest that first erupted in the south of the country has now engulfed the north - near the border with Turkey - and is threatening to spread eastwards towards its border with Iraq.
State television showed pictures of troops moving into Maarat al-Numan, which is some 40km (25 miles) south-east of Jisr al-Shughour, the town overrun by tanks and troops on Sunday.
It said the army had also moved into Khan Sheikhoun, just south of Maarat al-Numan, to prevent what it called "armed terrorist organisations" from cutting off the highway.
Officials said they were planning a "limited military operation" in Maarat al-Numan to restore security there.
One resident told BBC Arabic the town was very tense. "A sense of fear dominates the atmosphere just because the security forces and thugs are there. As soon as they disappear or leave, the city returns to normal," he said.
Another said there were "no more than 7,000 people" left in Maarat al-Numan, which has a population of 90,000 people.
According to the Syrian Observatory for Human Rights, thousands of residents were fleeing from the towns as troops approached.
At least 9,000 Syrian refugees have now fled across the border into Turkey, and Ankara says it will supply humanitarian aid to some 10,000 people who are stranded on the Syrian side of the border.
In its report published on Thursday, the UN said that the use of live ammunition against mostly unarmed civilians had killed around 1,100 people.
Syrian rights groups put the overall death toll in Syria at 1,297 civilians and 340 security force members.
UN investigators, who were refused access to the country, believe that as many as 10,000 people have been detained. The authorities appear to have denied civilians the right to food and medical care by laying siege to towns and preventing supply deliveries, it adds.
UN High Commissioner for Human Rights Navi Pillay has repeatedly appealed to Syria to let in a humanitarian team make a proper assessment, but the Syrian authorities have refused.
Meanwhile, Syria has called on the people of Jisr al-Shughour to return, saying things are back to normal following the 5army operation to restore government control there.
The Syrian Red Crescent has been asked to work with its Turkish counterpart to repatriate those who fled across the border, but the movement still seems to be in the opposite direction, the BBC's Jim Muir in Beirut reports.
Syria has prevented foreign journalists, including those from the BBC, from entering the country, making it difficult to independently verify reports from there.