In a Saturday statement, spokesman Mahmoud Afifi denounced the ongoing aerial bombardment of hospitals and civilians in Aleppo.
“The random airstrikes and barrel bomb attacks and the inhuman siege in eastern Aleppo are tantamount to war crimes,” he said.
The spokesman described the humanitarian situation in eastern Aleppo as “unbearable”, going on to call for an immediate ceasefire to allow humanitarian aid into the city.
Since Sept. 19, when the Bashar al-Assad regime announced the end of a week-long truce sponsored by Washington and Moscow, Syrian and Russian warplanes have pounded opposition-held parts of Aleppo.
Scores of civilians have reportedly been killed or injured in the attacks, which remain ongoing.
Syria has been locked in a vicious civil war since early 2011, when the Assad regime cracked down on pro-democracy protests -- which erupted as part of the "Arab Spring" uprisings -- with unexpected ferocity.
The Syrian Center for Policy Research, a Beirut-based NGO, has put the total death toll from the five-year conflict at more than 470,000.