Air strikes by Syrian regime ally Russia killed 10 civilians in the jihadist-held northwestern region of Idlib on Friday, a monitor said, as unsuccessful peace talks ended in Kazakhstan.
The raids killed three civilians including a boy on the outskirts of the town of Kafranbel, and seven including a girl in the town of Tal Hawash, the Britain-based Syrian Observatory for Human Rights said.
Syria's civil war has killed more than 370,000 people since it started in 2011, and endless rounds of negotiations have failed to stem the bloodshed.
The Damascus regime has won back large parts of the country from rebels and jihadists since Russia intervened in the war in 2015.
But several key areas remain beyond government reach, including Idlib, which is controlled by a former al-Qaeda affiliate.
Russia and rebel-backer Turkey in September inked a buffer zone deal to prevent a massive regime offensive on Idlib and nearby regions, close to the Turkish border.
But the area, currently home to some three million people, has come under increasing bombardment since jihadist group Hayat Tahrir al-Sham took full control of it in January.
The latest air raids came as two days of talks on ending the war in Syria -- sponsored by Russia, fellow regime ally Iran, and rebel backer Turkey -- concluded in Kazakhstan.
In a statement released after the meeting, the three countries expressed concern about HTS extending its influence in Idlib.
They stressed their "determination to continue cooperation in order to ultimately eliminate" HTS and the Islamic State group, the statement said.
US-backed forces expelled IS from the last patch of their 2014 "caliphate" last month, but the jihadists still have a presence in the Syrian desert and sleeper cells elsewhere.
'200 dead since February'
The United Nations has expressed worry over the new wave of bombardment on the Idlib region, around which a buffer zone was never fully implemented.
"I am alarmed by the recent escalation of violence and hostilities in and around the demilitarised zone in north-western Syria," the UN regional coordinator for Syria, Panos Moumtzis, said Thursday.
"Since February, over 200 civilians have reportedly been killed in Idlib," he said.
The fighting had also resulted in 120,000 people fleeing to areas closer to the Turkey border, he added.
Syria's war has displaced millions since it began with the repression of anti-government protests in 2011.
The talks in Kazakhstan Friday ended without notable progress on forming a committee to draw up a post-war constitution for the country.
The meeting had broached the issue with UN Special Envoy for Syria, Geir Pedersen, but further talks in Geneva would be needed, the joint statement said.
The parties were committed to "the establishment and the convening of the Constitutional Committee at the earliest in Geneva, holding the next round of consultations in Geneva" and supporting UN efforts, it read.
But talks in Kazakhstan would also continue, with Syria's neighbours Iraq and Lebanon to be invited to the next round of talks in July.
Jordan and the United States have observed the talks in the past.
After years of failed UN-led negotiations to end the war, Russia has taken a lead role in diplomatic efforts through the so-called Astana process.
The capital of Kazakhstan was called Astana until last month, when it was renamed Nur-Sultan after the country's outgoing president.