World Bulletin / News Desk 

Syrian oppositions began a major offensive to gain full control of the divided northern city of Aleppo, a monitor and its members said on Thursday.

The fall of Syria's main commercial hub would be a major blow for Bashar al-Assad, restricting his control mainly to a belt of territory stretching north from Damascus to the Mediterranean coast.

A statement by the groups said their goal was to "liberate the city of Aleppo" and to ensure that when it fell into their hands it would be ruled by strict sharia principles.

The British-based Observatory for Human Rights said a coalition of groups that included al Qaeda's Syrian offshoot Nusra Front and Salafi Ahrar al Sham had fired hundreds of mortar bombs on locations in western districts of the city that are held by the Syrian army and allied militias.

Much of the fighting was focused on the Jamiyat al-Zahra frontline, according to Rami Abdul Rahman, the head of the rights group which tracks the war.

But the fighting also spread across other frontlines, including the old city and a main army supply route into its portion of the sprawling city, Abdul Rahman added.

The Syrian army last month repelled a push by an alliance of rebels, including recipients of Western aid fighting under the name of the Free Syrian Army, into Aleppo's Rashidin district.

It was the first oppositions advance into the heart of Aleppo's government-controlled residential area in more than two years.