Live footage beamed on Aljazeera showed the night sky incessantly lit up as strike after strike hit mainly the Golan district of the city on Tuesday.
Aljazeera's correspondent reported a heavy exchange of gunfire was also heard and several homes were on fire.
Amid the explosions, Quranic recital could be heard over a mosque's loudspeaker, as a reminder to people to remember God at this time, the correspondent said.
He added that US marines were not only attacking from the air with helicopter gunships and warplanes, but ground troops were using machine guns and tanks as well.
There are reports that an AC-130 gunship aircraft fired multiple cannon rounds over the city. One report said the gunship fired 20 to 25 rounds at a time with explosions on the ground sending showers of sparks and flames into the night sky.
"I can hear more than 10 explosions a minute. Fires are lighting the night sky," one witness told Reuters. "The earth is shaking under my feet."
The fighting came hours after a US deadline for fighters in the city of 300,000 to hand over their weapons. More than 600 people have been killed since US marines besieged the city on 5 April.