India, Jan. 9 -- ALEPPO, Syria, January 9 - Syrian army forces have entered buildings in the Kurdish-majority districts of Sheikh Maqsoud and Ashrafieh in Aleppo, marking a serious escalation in three days of heavy clashes. The fighting between government troops and the U.S.-backed Syrian Democratic Forces (SDF) has derailed a major peace agreement and caused significant civilian casualties.

A Syrian military source told Al Jazeera that the army began concentrated artillery strikes on SDF positions in the two districts. The SDF media office stated government forces have bombarded residential areas for three straight days with artillery and tanks. Syrian state news agency SANA reported the SDF shelled the al-Midan neighbourhood in respons...