Rebel forces have taken control of the 'majority' of Syria's Aleppo city, as per UK-based monitoring group Syrian Observatory for Human Rights (SOHR).

The governor of Aleppo and the leadership of police and security branches withdrew from the centre of the city, and regime forces and reinforcement escaped from the city to Al-Safirah area, read the SOHR website.

Triggering conflict, a rebel alliance launched a surprise attack this week.

It is the first time Syrian rebels have entered Aleppo city since the government forces regained control over the region during the 2016 Civil War.

By Saturday morning, rebel fighters had taken control of large swathes of the city, according to footage geolocated by American news channel CNN.

The rebels reportedly faced limited resistance from Syrian forces.

Several residents inside Aleppo told CNN that there has been minimal fighting in the city’s urban areas.

Kurdish forces have also expanded their control of some neighbourhoods of Aleppo, residents told the news channel.

As per Syrian Observatory for Human Rights website, a Russian fighter jet launched an airstrike with three missiles on military headquarters that included a group of members of the “Joint Forces” of the Turkish-backed “National Army”, on the outskirts of Marae’ City in northern Aleppo countryside.

The website claimed over 300 people died since the offensive started on Wednesday.

Armed conflicts have been going on in Syria since 2011.

Separate terror groups have been operating in various parts of the nation ever since the army liberated most parts of the country.