In continued fighting, five people have died and nine injured, one of them a child, over the past 24 hours, the council said.
Its warning comes amid reports that artillery and mortar strikes had demolished a power substation and damaged high-voltage electric transmission lines. Power and water supply are reported out of action, more than 4,000 families left without gas, and land lines and cell phones not functioning.
Reports say shelling destroyed a school and supermarket and ruined the local history museum's roof. Four unexploded devices were found in the city since Thursday.