Fighting intensified in the Syrian city of Aleppo over the weekend, with the government of President Bashar al-Assad deploying troops and aircraft to retake neighborhoods captured by opposition militants in a major offensive last week.

There were reports of heavy fighting in the historic city center and old fort areas of Aleppo, Syria’s most populous city and its main commercial center. The BBC, which has a correspondent inside the city, reported that the Syrian army was shelling militia positions in the suburb of Salah al-Din, and that thousands of civilians are fleeing Aleppo.

While the rural districts around Aleppo have experienced frequent clashes between government forces and opposition militants during the sixteen-month civil conflict, the city had until recently seen relatively little violence. However, there have been a growing number of deadly attacks on government facilities and personnel in Aleppo this year, with anti-Assad fighters strengthened by increased weapons supplies flowing across the border from neighboring Turkey.

In response to the fighting in Aleppo, Sayda Abdulbaset Sayda, the leader of the US-backed Syrian National Council, urged the West and the Gulf monarchies to increase their support to the opposition militias. “We want weapons that would stop tanks and jet fighters,” Sayda said during a visit to the United Arab Emirates.