The UN says it is concerned over the escalation in fighting near the Syrian capital ahead of peace talks due to resume in Geneva. Syria was also on the agenda of the visit to Turkey of US Senator John McCain.
Air strikes in the Syrian capital of Damascus on Monday killed at least seven people and wounded several others, the Syrian Observatory for Human Rights said.
The latest air bombardment marks a third straight day of escalation in attacks by Syrian regime forces and their allies on rebel-held neighbourhoods in the capital.
The United Nations said the escalation in fighting is worrying as peace talks on Syria are due to resume in Geneva on February 23 after a nearly year-long break.
"There have been reports of civilian deaths and injuries from shelling in Qabun, Barzeh, Tishreen and western Harasta districts of the city of Damascus," UN spokesman Farhan Haq said on Monday.
"The UN is alarmed by the intensification of fighting in the Damascus area in recent days."
Turkish forces and the US-backed opposition killed at least 44 Daesh militants in northern Syria in the last 24 hours, the Turkish General Staff said on Tuesday.
The military said Turkish land and air forces had hit 109 Daesh targets, including shelters, as part of Operation Euphrates Shield, launched in August 2016 to secure Turkey's border with Syria.
One Turkish soldier was killed and two others injured clearing mines and improvised explosive devices (IEDs), the military said.
TRT World's Ediz Tiyansan has more from Hatay on the Turkish-Syrian border.
Turkish-US cooperation against Daesh
Daesh on Monday attacked the Free Syrian Army (FSA) in southeastern Syria near the Golan Heights, seizing several villages and a large town.
The advance by Daesh comes amid international plans of recapturing the group's last Syria stronghold and de-facto capital, Raqqa.
Monday's setback for the opposition came as the US and Turkey are increasing their coordination in the battle against Daesh.
The CIA's chief and a top US Army general visited Turkey last month to discuss Syria and a possible strategy to clear Raqqa.
Republican Senator John McCain was in Turkey on Monday and met President Recep Tayyip Erdogan.
"The United States must work with Turkey to deal a rapid and lasting defeat to ISIL [Daesh] as part of a broader strategy to strengthen US allies and partners, counter the malign influence of our adversaries, and build a favourable balance of power in the region," McCain said following his meeting with the Turkish president.
CIA-coordinated military aid for Free Syrian Army (FSA) rebels in northwest Syria has been frozen since rival factions attacked them last month, rebel sources said, raising doubts about foreign support key to their war against the Assad regime.
Reuters confirmed the freeze with officials from five of the FSA groups that have been recipients of financial and military support from the so-called "MOM operations room." It was also confirmed by two other senior FSA figures briefed on the matter.
They spoke on condition of anonymity given the covert nature of the CIA-backed programme and the sensitivity of the subject.
Rebel officials told Reuters that no official explanation had been given for the move this month following the assault, though several said they believed the main objective was to prevent arms and cash falling into enemy hands. But they said they expected the aid freeze to be temporary.
"The reality is that you have changes in the area, and these changes inevitably have repercussions," said an official with one of the affected FSA rebel groups. He said no military assistance could "enter at present until matters are organised. There is a new arrangement but nothing has crystallised yet".
The CIA declined comment on the reported freeze in support.