BEIRUT — An airstrike near the site of a suspected gas attack in Syria killed at least 10 civilians Wednesday, as U.S. Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov agreed to meet this week for extended discussions on ending the 5-year-old civil war.

Russia, a key ally of Syrian President Bashar Assad, has been conducting airstrikes to bolster his forces for nearly a year. The United States supports rebels fighting to overthrow Assad and has called on him to step down.

U.S. President Obama and Russian President Vladimir Putin failed to negotiate a settlement on the sidelines of the G-20 conference in China on Monday. Obama acknowledged “gaps of trust” between the rival powers following months of negotiations between their top diplomats.

The Russian Foreign Ministry said Lavrov and Kerry would meet Thursday and Friday in Geneva to work out the remaining details of a possible deal, following a phone call between the two. But U.S. officials indicated the earliest the talks could happen is Friday.

U.S. Defense Secretary Ash Carter said in London that Kerry would not be making another attempt with Lavrov if there were no prospects for success, but he added: “We’re a long way from getting there.”

Moscow warned that Turkey’s incursion into northern Syria was complicating peace efforts, underscoring that the operation has not been sanctioned by the U.N. Security Council or the Syrian government. Turkey’s actions “could further complicate the military and political situation in Syria, which is dire as it is” and jeopardize international efforts to reach a peace deal, it added.

Turkey pushed into northern Syria two weeks ago to expel the Islamic State group from its border and halt a northward advance by Syrian Kurdish forces, which Ankara sees as an extension of an outlawed Kurdish separatist group inside its own borders.

Deputy Prime Minister Nurettin Canikli said Turkey would like to create a no-fly zone over the area to repatriate Syrian refugees.

The airstrike Wednesday devastated the al-Sukkari neighborhood in the divided city of Aleppo. Video from the local branch of the Syrian Civil Defense search-and-rescue organization showed residents yelling for help as first responders dug victims out of the rubble. At least half a block appeared to be destroyed.

Medical workers said the opposition-controlled neighborhood was hit Tuesday with chlorine gas, though the report could not be independently verified. They said they treated at least 70 people for breathing difficulties. A 13-year-old girl and a 29-year-old man died from further complications Wednesday.

Mohammed Abu Jaafar, head of a forensic department in the rebel-held part of Aleppo, said the teenager had died of suffocation and respiratory burns.

Chlorine gas is a crude weapon that can be fatal in high concentrations. In lower doses, it can damage lungs or cause severe breathing difficulties and other symptoms, including vomiting and nausea.