At least 53 people have been killed in a ferocious attack on a market in northern Syria that left rescuers and survivors digging late into the evening to search for residents buried under the rubble.

There were at least three air strikes on the market at Atareb, a town in the Aleppo countryside swollen by the arrival of refugees from nearby battles, in the latest breach of a “de-escalation” agreement that has proven largely unenforceable.

Aleppo, Syria’s largest city, is controlled by the government.

The attack tore market-goers apart, according to media published by the activist-run Thiqa news agency. A police station by the market was also struck, killing an officer, according to the Britain-based Syrian Observatory for Human Rights monitoring group.

At least 53 people were killed according to the Observatory, which said the market was hit by three separate strikes. There were at least five children and three women among the dead.

Damage following air strikes in Atareb, SyriaDamage following air strikes in Atareb, Syria (Thiqa News via AP)

The Observatory said it could not determine whether the Syrian government or its chief backer, Russia, was behind the attack.

Thiqa said at least 47 people were killed and more than 90 wounded.

Atareb and the countryside around it remain outside the control of the Damascus-based government which says it wants to retake all of Syria following six years of civil war that has killed at least 400,000 people and displaced 11 million others — half 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, the Islamic State group, nearing defeat, the two superpowers 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 two countries said “de-escalation areas” were an “interim step” towarda restoring peace in Syria and that there could be “no military solution” to the war.

It drew a sarcastic response from Turkish President Recep Tayyip Erdogan, who said the two superpowers could start by withdrawing their own troops from the war and instead support holding elections in Syria.

He said there were five Russian and 13 US bases in Syria, plus a 14th under construction in the northern city of Raqqa, now administered by a US-backed Kurdish party that Turkey says is an extension of a separatist group operating within its own borders. Turkey considers the group a terrorist organisation.