Syria’s opposition coordinator Riad Hijab told reporters during a teleconference that Syrian regime forces backed by Russian air strikes committed a “massacre” of scores of civilians in Idlib on Monday, part of a pattern of violation of a two-week truce.
Hijab said that the latest attacks, as well as arrests by regime forces, were making the opposition consider whether it should attend a round of peace talks in Geneva.
"It will be before the end of this week, there will be a clear decision about this," Hijab said.
At least 15 people were killed and more than 30 were injured after warplanes conducted three air strikes which hit a main bazaar and two other residential areas in the opposition-held town Abu Aduhur in Idlib province on Monday.
The air strikes were carried out by Syrian regime forces, according to the Turkish Anadolu Agency.
On Sunday, at least nine civilians were also killed and dozens were injured after around one hundred mortars and rockets were fired on a mainly Kurdish residential quarter in Syria's northern city of Aleppo.
The UK-based Syrian Observatory for Human Rights, which tracks violence in Syria, confirmed the attack and said that it was among the biggest allegedly carried out by Al Qaeda's Syrian offshoot Nusra Front in the area, which also adjoins state-run parts of Aleppo.
A number of Syrian opposition groups as well as the regime had agreed to decrease tensions as the international community seeks to push through a transition phase to finally end the five-year-long conflict that has ravaged the country.
However, the agreement does not include Nusra Front and DAESH terrorist group.