The raids, believed to be carried out by either Syrian or Russian jets, targeted Maarat al Numan, a densely populated city in southern Idlib province –– a de-escalation zone –– leaving a trail of destruction and carnage, rescuers say.
Air strikes killed 50 people in northwest Syria on Monday, most of them in a crowded market, a war monitor reported, in the latest violence to plague the opposition bastion.
Thirty five civilians and two unidentified people were killed in raids that hit the vegetable market and surrounding areas in the town of Maaret al-Numan in Idlib province, while six more were killed in regime air strikes on the nearby town of Sarqib, said the Syrian Observatory for Human Rights.
More than 100 others were wounded, according to the Britain-based monitor.
"Bodies are lying on the streets. May God take revenge on (Russian President Vladimir) Putin and (Syrian President Bashar Assad) for their crimes," Abdul Rahman al Yasser, a rescuer from Idlib's civil defence team White Helmets searching for bodies under the rubble, told Reuters.
White Helmets volunteer Amir Al Bunni, father of two, also died in the air strikes.
Anas al Dyab, a citizen journalist working with AFP and volunteering for the Helmets died in an attack on Sunday.
While the world is waking up to life, Amir was killed while waking up to devastating airstrikes on Maarat AlNuman.— The White Helmets (@SyriaCivilDef) July 22, 2019
Amir Al-Bunni, a White Helmet volunteer and a father of two young boys, Mohamad and Saif, was killed while responding to attacks on #MaratAlNuman city this morning. pic.twitter.com/cUMIsrVVJa
Death toll expected to rise
At least 45 other people were wounded in the air raid that hit "a wholesale vegetable market in the town of Maaret al Numan," the Syrian Observatory for Human Rights said.
The death toll could still rise as many of those wounded are in a critical condition and some people are still trapped under rubble, the Britain-based monitor said.
Observatory head Rami Abdelrahman said 16 of those killed were civilians while three other bodies remain to be identified.
Turkey and Russia agreed last September that Idlib would remain a de-escalation zone in which acts of aggression are expressly prohibited.
The Syrian regime, however, has consistently broken the terms of the ceasefire, launching frequent attacks inside the de-escalation zone.
Busy marketplaces and residential areas have been a frequent target of the campaign waged by Russia and Syria on Idlib and Hama since the end of April.
The renewed assaults on civilian areas have killed hundreds, rescuers said.
Residents and local and international aid agencies that support the opposition and rebel-held areas say the sustained campaign paralysed everyday life in opposition areas.
According to an Anadolu Agency correspondent, Russian and regime warplanes also carried out attacks on the town of Bidama and the villages of Talmenes and Al Kabina.
Monday's deaths bring the toll to 40 in the past 24 hours as 17 civilians were killed in Russian airstrikes in the same de-escalation zone on Sunday.
The Russian-backed offensive has so far failed to make major inroads into territory in northern Hama and southern Idlib provinces, where the mainstream opposition backed by Turkey is putting up fierce resistance –– alongside militants also battling the Assad regime's oppression in Syria –– in their last remaining bastion there.
Russia and the Syrian army deny allegations of indiscriminate bombing of civilian areas and say they are fighting al-Qaeda-inspired militants.