A hardline Islamist rebel group announced on Tuesday the start of a battle to break the regime siege of rebel-held districts of Syria's second city Aleppo.

Ahrar al-Sham, a leading rebel Salafist faction active in the northern provinces of Aleppo and Idlib and allied to the Al-Qaeda-affiliated Al-Nusra Front, issued the declaration on Twitter.

It announced "the beginning of the battle to break the siege of the city of Aleppo with the liberation of military positions in Al-Mallah district". 

President Bashar al-Assad's forces have controlled the southern part of the district since July 7, when they cut a key route threatening the supply of food and other essentials to 200,000 people, said the Syrian Observatory for Human Rights.

Several Islamist groups have since launched attacks to try to halt the regime advance, but so far without any success.

Aleppo city was once Syria's economic powerhouse, but it has been ravaged by the war that began in March 2011 with anti-government protests.

The conflict has killed more than 280,000 people and left Aleppo divided roughly between government control in the west and rebel control in the east.

Source: AFP