If the reports coming from the city are correct, that would bring the death toll since the weekend to 200, The New York Times said. Activists say Hama is now isolated, with no landline, cellphone or Internet connections and only satellite telephones linking it to the outside.
A man who said his name was Abu al-Walid spoke to al-Jazeera.
"The situation is very difficult," he said. "The lack of electricity has spoiled food supplies. They are shelling the city around the clock."
While his military is cracking down on Hama, President Bashar Assad has been offering a more democratic Syria. The president has approved a multiparty political system, Syrian media said Thursday, as Washington put new sanctions on Syria for its brutal crackdown.
Assad's decree grants citizens the right to establish political parties with the aim of contributing to political life "through peaceful and democratic means," the state-run Syrian Arab News Agency reported.
The Syrian opposition dismissed the decree, alleging it was simply for show and would produce no real change.
Assad's promised new rule of law came as Syrian forces once again shelled Hama and plainclothes gunmen shot people in the streets in the fifth day of a tank, armored vehicle and sniper assault on the rebellious city, residents and activists said.
Hama, a city of 700,000 north of Damascus whose name means "fortress," has emerged as a linchpin of the nearly five-month uprising.
The U.S. sanctions against Syria announced Thursday were the latest in a series seeking to isolate Assad and his close aides, the Treasury Department said.