Syrian state television says troops arriving in the city of Homs were given a rapturous welcome by local residents.
It broadcast pictures showing people lining the streets and waving Syrian flags as the military convoy drove into the country’s third largest city.
A day earlier, government tanks were said to have shelled a residential district. At least six people were reported killed in Homs and another dozen were said to have died in Deraa.
Images posted on the internet are said to show the trouble in Homs unfolding. There are scenes of confusion as a large crowd is apparently scattered by gunfire. A tank can be seen and automatic gunfire is heard.
A human rights and opposition figure who has met government officials says he has been assured that troops will not fire on demonstrators if, as expected, crowds gather after Friday prayers.
However security forces have been tightening their grip on other towns.
Friday prayers offer the only chance for people to gather in large numbers lawfully, and troops and tanks are said to be getting ready.
The Geneva-based International Commission of Jurists has accused Syrian forces of indiscriminate shelling and of rounding up thousands of people during the country’s two-month uprising.
The authorities blame the violence on “armed terrorist” groups.