AFP reports that at least 35 people have been killed during the ongoing fighting between pro-government forces and al-Nusra Front forces.
"Fierce fighting raged past midnight (Sunday) on several fronts in the south of Aleppo province," said the British-based Syrian Observatory for Human Rights (SOHR) in a statement.
"Shelling and fighting in the past 24 hours has left 19 Syrian and non-Syrian members of Al-Nusra dead... while 16 pro-regime fighters were also killed," SOHR placed the number of confirmed dead at 35, though indicated that the death toll could continue to rise.
The US and Russia backed a truce in Syria that began on February 27. Militant groups, such as Daesh and the al-Qaeda-affiliated Nusra Front, are not under the terms of the truce.
"Al-Nusra, (Islamist rebel group) Ahrar al-Sham and their allies are pushing an offensive to take back turf seized around Aleppo by the regime before the truce came into force," SOHR director Rami Abdel Rahman told AFP.
Air raids and barrel bombs from the Russian-backed Syrian regime forces continue to strike targets in and around Aleppo. Reports indicate that at least one Nusra Front militant is believed to have set off a suicide explosion.
"The violence around front lines has by no means stopped," he added.
Civilian casualties are unknown.
