Western powers have expressed alarm over the government's campaign against Eastern Ghouta, where 400,000 people have been besieged since 2013, facing severe food and medicine shortages.
Rescue teams rushed to Jisreen and pulled three children and a woman out of the rubble.
In Damascus, the official SANA news agency said the local fighters were battling militants from the so-called Islamic State and the US -backed SDF in the area.
The United Nations has been sounding the alarm about the escalating level of violence, and called on Tuesday for a humanitarian truce of at least one month to allow for aid deliveries and evacuations of the wounded.More news: Oregon State hits 18 three-pointers to beat Washington women 95-57
The Israeli air force said it has air sorties against more than 100 Syrian arms convoys and vehicles belonging to Lebanon's Shiite militia Hezbollah, which is fighting alongside Assad's forces, since the Syrian Civil War began more than six years ago.
Syria's state media say the USA -led coalition has bombed government-backed troops in eastern Syria, citing reports of dozens killed and wounded.
The PKK is designated as a terrorist group by Turkey, the USA and the EU.More news: North and South Korea parade together at Winter Games 2018
At least two civilians were killed in retaliatory rebel mortar fire on government-controlled areas of Damascus, according to state news agency SANA. However, Anadolu Agency earlier reported that the helicopter crashed in the southern Turkish province of Hatay. The jihadist group, Hayat Tahrir Al Sham (HTS), the latest incarnation of the former Al Qaeda affiliate, militarily dominates the province. In the battle, Turkey is relying on Syrian rebel forces that have lost all their other worldwide backers.
More than 800 civilians are believed to have been injured in the same period. After two days of discussions, the congress, brokered by Russia, Iran and Turkey, reaffirmed its full commitment to the "sovereignty, independence, territorial integrity and unity" of Syria.
US National Security Adviser H.R. McMaster held talks with Turkish President Recep Tayyip Erdogan on Sunday amid persistent tensions between the North Atlantic Treaty Organisation allies over Syria and other issues. The official spoke on condition of anonymity because he was not authorized to talk to the media.
It was not immediately clear when the Istanbul meeting would take place.
Eastern Ghouta and Idlib, a northern province where violence also flared this week, are both so-called de-escalation zones agreed previous year in a bid to pave the way for an end to the conflict.More news: Australian sites among thousands hacked to include mining script
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