Syrian Observatory for Human Rights (SOHR) reported on Thursday that opposition groups in Syria launched hundreds of rockets and missiles to seize regime-held areas in Aleppo.
The rights group announced that four civilians had been killed and over 70 were injured while five rebels died in the clashes with forces loyal to Bashar Assad.
The rebel groups said their goal was to "liberate the city of Aleppo" and to make certain the city would be ruled by sharia principles after the control was taken, in a statement.
Rami Abdul Rahman, the head of SOHR, said most of the fighting took place on the Jamiyat al Zahra frontline, where rebel groups attacked the district which is controlled by the Assad forces.
A new alliance of rebel groups called Ansar Sharia is allegedly behind the attack, including the Al Qaeda affiliated Nusra Front.
Aleppo is the country’s largest city and biggest industrial and financial centre.
The control of the city is divided between regime and rebel forces since the war in Syria which began in 2012.
While the Assad regime controls areas in the western part of the city, different rebel groups exist in the eastern part.
The fall of Syria's largest city would be a major blow for Assad, according to analysts.
After the war flared up in Aleppo, the commercial capital of Syria, in 2012, the city was divided into two parts with Assad regime forces continually losing ground to opposition groups.
Last year, at least 3,000 civilians were killed in Aleppo by Syrian regime barrel bomb attacks, according to Amnesty International.
More than 220,000 people have been killed in Syria since March 2011, and more than 1 million have been wounded since the armed conflict started in 2012, according to United Nations estimates.