Monitoring groups and activists said at least 15 people were killed and more than 30 were injured after warplanes conducted three air strikes which hit a main market and two other residential areas in the rebel-held town Abu Aduhur in northwestern Idlib province.
The report added that air strikes caused mass destruction in the town.
A regime warplane struck a fuel market in Idlib, killing 15 people and injuring 40 others, civil defence sources told Anadolu Agency.
The attack has left several shops in flames, the sources said.
Syrian activists posted a footage online which shows air strikes' aftermath in what they claimed is the market in Abu Duhur. A man appeared in the footage saying that there is no Nusra Front in the area, the whole of the casualties are civilians. Residents claim that the air strikes were conducted by Russian warplanes.
The town of Abu Duhur was captured by opposition forces in 2012, since then the area has been a place for confrontations between them and Syrian regime forces.
The UK-based Syrian Observatory for Human Rights said at least nine civilians were killed and dozens others were wounded when around 100 mortars and rockets were fired at a mainly residential quarter in the northern city of Aleppo.
The rights group said the attack was among the biggest allegedly carried out by Al Qaeda's Syrian offshoot Nusra Front, the area 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 Nusra Front and the DAESH terrorist group were not included in the talks.
Geneva peace talks
The recent escalations comes as the main Syrian opposition council stated that they will go to the talks which the United Nations aims to convene in Geneva "God willing" and wants an immediate start to negotiations on a transitional governing body, a spokesman for the council told Reuters on Monday.
"Our inclination is to go," Riad Nassan Agha, a member of the High Negotiations Committee (HNC), said, adding that violations of a cessation of hostilities agreement on the part of the Syrian regime and its allies had reduced in the last two days.
He said people would start arriving in Geneva on Friday, cautioning that the HNC hoped nothing would happen that would prevent them from going to the talks.
"We started to notice that the volume of violations has started to reduce in the last two days. We hope that in the coming days until Friday that the violations reach zero," he said. "If these violations end this will create the favourable environment for the start of negotiations."
The war-torn country has been watching a fragile process of a cessation of hostilities since Feb. 27 following a major agreement brokered by US and Russia.
Syria is currently in a full blown civil war between five main factions - the regime, the opposition, Al Qaeda affiliate Nusra Front, DAESH, and the YPG militants.
According to recent estimates from the Syrian Observatory for Human Rights, the war in Syria has claimed the lives of more than 470,000 people.
The Syrian Network for Human Rights has reported that more than 180,000 civilians have died from the start of the war till January 31 this year.
About 5 million others took refuge in the neighbouring countries of Turkey, Lebanon, Iraq and Egypt, with Turkey hosting the largest number with almost 2.7 million.
Thousands are still pushing towards European countries which has caused a crisis for the continent.