Syrian forces blitzed areas in and around the northern city of Aleppo on Friday, Aug 24, activists said, as Western powers sought to tighten the screws on embattled President Bashar al-Assad, AFP reports.

France said it backed a partial no-fly zone over Syria, where the regime is intensifying its attacks from the air as it battles to stamp out rebel strongholds in Aleppo and pockets of resistance in the capital Damascus.

New envoy Lakhdar Brahimi was due to meet UN chief Ban Ki-moon later Friday on the 17-month conflict that has escalated from a peaceful uprising against Assad's rule into an increasing bloody civil war.

France and Germany said they are pushing for UN Security Council action on the humanitarian crisis as the number of refugees soars above 200,000, while over 2.5 million are in need of aid inside the country, according to the UN.