Activists talking to Al Jazeera in the early hours of Saturday said the army had used mortars and nail bombs in the assault on the Khaldiyeh neighbourhood.
Hundreds were reported injured, and a doctor in a hospital told Al Jazeera that there was an urgent need for blood as medics were struggling to attend to the injured.
“We cannot confirm the exact number of the martyrs. There are many killed,” Hadi al-Abdallah, an activist in Homs, told Al Jazeera.
“A building of 16 flats has collapsed. We’re trying to get the bodies out of the rubble.”
Abdallah said army defectors had captured 19 members of the security forces earlier in the day.
Homs is one of the flashpoint cities in Syria’s uprising, with some areas becoming strongholds of the armed opposition.