On Friday Hama saw some of the biggest demonstrations yet against President Assad Syrian tanks and troops are being deployed in the restive city of Hama after the sacking of its governor, reports say. Troops are said to be taking up positions at key entrances to Hama, and in the city centre.
There are reports of gunfire and mass arrests taking place.
On Friday the city saw some of the biggest demonstrations yet against the rule of President Bashar al-Assad.
A day later, Mr Assad sacked the governor of Hama, Ahmad Khaled Abdel Aziz.
Activists say more than 1,350 civilians and 350 security personnel have been killed across Syria since protests began in mid-March.
'Military solution' Rami Abdel-Rahman, president of the Syrian Observatory for Human Rights, said troops took up positions at Hama late on Saturday and "heavy gunfire" was heard in the city overnight.
He told Reuters news agency there had been a number of arrests on the outskirts of the city.
"The authorities seem to have opted for a military solution to subdue the city," he said.
Tens of thousands of people were said to have taken part in protests in Hama on Friday.
The BBC's Owen Bennett-Jones, in the Lebanese capital Beirut, says there were reports that the army had eased its presence in the city earlier in the week, but the authorities now seem to be using overwhelming force.
Hama was the scene of a Muslim Brotherhood uprising against Mr Assad's father, Hafez, in 1982, which the army crushed, killing at least 10,000 people.
The Syrian government has not commented on its latest military movements.
Mr Assad has previously accused a "small faction" of "saboteurs" of exploiting popular grievances.
Reports cannot be independently verified as the Syrian authorities have banned most foreign media from the country.