Syrian army helicopters and troops shelled rebel positions in the country's largest city Aleppo on Saturday.
Reuters reported that Syrian troops breached the rebels' frontline by firing artillery shells in the battleground district of Salaheddine.
ITV News' Neil Connery reports:
In the air, helicopters fired rounds of bullets to break through the insurgent front line.
A Reuters reporter, based in the city, said that two explosions were heard "every minute".
Earlier Syrian forces clashed with rebels close to Aleppo's television and radio stations, according to activists.
A local rebel commander was reported as saying that his fighters were preparing for a "strong offensive" by government forces on the city.