At least 53 people have been killed in three airstrikes on a Syrian market.
The ferocious attack has left rescuers and survivors digging late into the evening to search for residents still buried under the rubble in Atareb.
The town in the north of the country, has seen an influx of refugees following the battle to retake Aleppo - which is around 20 miles east of Atareb - and other nearby battles, in the latest breach of a "de-escalation" agreement which has proved largely unenforceable.
Activist-run Thiqa news agency reported that the attack "tore market-goers apart", while the British-based Syrian Observatory for Human Rights reported that a police station by the market was struck in the attack, killing a police officer.
The monitoring group continued that among the dead were at least five children, while Thiaq put the number of wounded at more than 90.
The Observatory continued that it did not know if the Syrian Government, or its chief backer, Russia, was behind the attack.
Despite its proximity to government-held Aleppo, Syria's largest city, Atareb and the countryside around it remain outside the control of Damascus which says it wants to retake all of the middle-eastern country following six years of civil war that has killed at least 400,000 people and displaced 11 million others - half of the country's population.
The war began after a violent crackdown against demonstrations calling for reforms in 2011. It has drawn in fighters from across the world.
President Bashar Assad says he is fighting a war on terror.
Moscow's intervention on the side of Assad in 2015 turned the tide in his favour.
Atareb and the opposition-held countryside in north-west Syria are meant to be protected by a "de-escalation agreement" brokered earlier this year by Russia, Iran, and Turkey, the main backers to the Syrian government and the opposition.
The US and Russia have recently renewed efforts to find a settlement for post-war Syria.
With their common enemy, so-called Islamic State group, nearing defeat, the two countries find themselves again on opposite sides of the conflict, with Moscow backing Assad and the US offering rhetorical support to armed opposition groups fighting the government.
In a joint statement on Saturday, the US and Russia said "de-escalation areas" were an "interim step" towards restoring peace in Syria and that there could be "no military solution" to the war.
In response, Turkey's President Recep Tayyip Erdogan, said Russia and the US should start by withdrawing their own troops from the war and instead support holding elections in Syria.
Also on Monday, Amnesty International released a report saying that under so-called "reconciliation" agreements, government sieges and intense bombardments of some rebel-held areas in Syria have given no choice for residents but to leave or die.
The report said the Syrian government and, to a lesser extent, armed opposition groups "have unlawfully besieged civilians, depriving them of food, medicine and other basic necessities, and carried out unlawful attacks on densely populated areas".