Nada Homsi and Anne Barnard

BEIRUT — A resurgence of deadly attacks by pro-government forces in de-escalation zones in Syria, including a triple airstrike on a busy marketplace that killed more than 50 people, is undermining an agreement portrayed by its sponsors as a crucial step toward ending the 6 1/2-year civil war.

The accord — reached this year between Russia and Iran, which are allied with Syria’s government, and Turkey, which backs some rebel groups — established four de-escalation zones where attacks were supposed to decrease and so help pave the way for a peace settlement.

The de-escalation zones encompass most of the remaining areas of Syria still held by insurgent groups, not including the Islamic State. Under the agreement, the combatants are to refrain from new attacks, except against hard-line groups that have not signed on to the pact. Long-standing sieges are to be lifted to allow free movement of goods and people.

But siege and bombardment tactics, mostly by the Syrian government against rebel-held areas, have continued despite the Astana accord, named for the Kazakh capital where it was struck. The recent uptick in attacks — and the lack of any outcry from international sponsors of the Astana deal — has bolstered skepticism from opponents of the Syrian government who doubted the deal’s good faith from the start.

This month, after a meeting in Da Nang, Vietnam, President Donald Trump and President Vladimir Putin of Russia issued a joint statement affirming the “importance of de-escalation areas as an interim step to reduce violence in Syria.”

But days later, on Monday, airstrikes hit a marketplace in the rebel-held town of Atarib, which is in a de-escalation zone in the northern Syrian province of Aleppo.

The marketplace was “completely destroyed,” said Ali Obeid, a witness who broadcast the aftermath on social media. His video and others showed desperation, suffering and bewilderment.

In one, a man paused next to someone he apparently recognised, whose head had been blown off. “God give your soul peace,” the man said. In another scene, a man called for help from the floor of a destroyed shop. He had lost a leg.

The attack came on the same day that Amnesty International issued a report condemning de-escalation zone violations and what it called the collective punishment of civilian populations in rebel-held areas.

Attacks in Atarib and elsewhere “highlight concerns about these so-called safe zones and whether they are really ever safe,” Rawya Rageh, a senior adviser to Amnesty who was a co-writer of the report, said in an email. “Time and again, civilians in Syria are finding no safe place to take refuge.”

With the world’s attention focused on other issues in the Middle East, like the escalating tensions between Saudi Arabia and Iran that have sparked a political crisis in Lebanon, there has been little official outcry about violations of the de-escalation zones, where many armed and unarmed opponents of President Bashar Assad are concentrated.

International leaders consider the de-escalation zones a building block as preparations are being made for a new round of U.N.-backed peace talks in Geneva this month between the Syrian government and the main opposition coalition, and for separate Russian-backed talks between Syrian factions in the Russian town of Sochi.

Countries that are hosting millions of Syrian refugees, including Lebanon, Turkey and Jordan, have cited those talks and the de-escalation agreement as reasons to press for the refugees to return home.

The agreement allows for attacks on a hard-line Islamist insurgent group, the al-Qaida-linked Levant Liberation Committee. The group is the most powerful one within the de-escalation zone that includes Atarib and the neighbouring province of Idlib, dominating more moderate groups calling themselves the Free Syrian Army.

But Atarib is not under the control of the Levant Liberation Committee. The town is known for its history of civil and armed resistance against both the Syrian government and hard-line Islamist groups. Its residents helped local rebels expel the Islamic State in 2014, and they drove out the al-Qaida-linked Nusra Front — a group that later morphed into the Levant Liberation Committee — after it tried to take over in 2015.

To Atarib residents, the attack bolstered a sense that the de-escalation agreement is failing to protect them, and highlighted the dissociation between international diplomacy and local reality.

“It is a norm now that the civilians are being targeted everywhere,” said Shady al-Mahmoud, an activist from Atarib, “and the international silence that follows such atrocities has become a norm as well.”

In recent months, airstrikes by the Syrian government or Russia have hit schools, hospitals and homes in Idlib and in the Damascus suburbs of Eastern Ghouta, another de-escalation zone, where the U.N. says 400,000 residents are trapped and where one in four children are at risk of malnutrition. A World Food Program warehouse in Eastern Ghouta was attacked this month. The other de-escalation zones encompass an enclave in Homs province in central Syria and a stretch of southern Syria that borders Jordan.

Further complicating the picture is the Syrian government strategy of forcing the surrender of rebel-held areas and offering people there the choice of returning to government control or being bused to rebel-held Idlib; some 20,000 people displaced that way have ended up in nearby Atarib.

“Tens of thousands of civilians have been forcibly displaced to opposition-held areas in the north under local deals after enduring years of unlawful siege and bombardment,” Rageh said. “They are essentially stuck and exposed as easy marks.”

Syria’s government has signalled reservations about the premise of the de-escalation deal. Ali Haidar, minister of reconciliation, said in an interview with Syrian state media that failure of the agreement would put all other options back on the table — including military force.

“The Syrian state has one option: to eliminate terrorism and the whole of terrorism and to restore any area of Syria,” he said.