Syrian government forces have begun an all-out ground assault on besieged rebel-held east Aleppo, as they attempt to retake the whole of the city.

Troops attacked from four fronts, in their first offensive inside the city since the opposition took hold in 2012.

They advanced towards the contested old quarter of Aleppo - home to the Umayyad Mosque, a UNESCO world heritage site and centerpiece of the city’s walled Old City.

There was also fierce fighting to the south of Aleppo, where rebels are battling pro-government troops to reopen the only route out for the some 250,000 residents on the eastern side who remain trapped.

For the past five days, Syrian and Russian warplanes have been bombing east Aleppo with an unprecedented ferocity.