The Syrian city of Aleppo has come under fresh bombardment, activists say, as the government attempts to retake districts seized by rebel fighters, - BBC reported. - "1TV"

Several areas of the city were reported to have come under attack, including strafing from helicopter gunships.

The rebels say they have completely withdrawn from the embattled Salah al-Din district "in a tactical move".

The fighting comes as Iran prepares to host its own international meeting on the Syrian crisis.

Iran, Syria's only regional ally, says it will be attended by countries with a "realistic" position on the crisis.

But it is unclear exactly which countries will be attending the summit, held in Tehran.

Western governments have expressed scepticism that Tehran can mediate, because of its close relationship with the government of Syrian President Bashar al-Assad.

A new prime minister, Wael al-Halqi - the former health minister - has been appointed, state television has announced.

He replaces Riad Hijab, whose defection to the opposition was announced on Monday and who was said to have crossed into Jordan on Wednesday.