German Chancellor Angela Merkel says she is "horrified" by the suffering being caused by Russian and Syrian air strikes.
Merkel, who was in Ankara for talks with Turkish officials, said on February 8 that "tens of thousands" of people are being affected by the bombing campaign that is coming "primarily from the Russian side."
She added that Germany and Turkey will insist on compliance with a UN resolution passed in December that calls for an end to the bombing of civilians.
Western nations have repeatedly accused Russia -- which began its Syria bombing campaign in September -- of targeting moderate opposition groups instead of Al-Qaeda and Islamic State (IS) fighters, and of killing hundreds of civilians in the western and northern parts of Syria.
The Kremlin denies the charges and says it is only bombing terrorist groups.
Russian air strikes have helped Syrian forces recapture some territory lost to extremist groups and other opposition fighters in central and western Syria.
Syrian forces in recent days have made gains in areas surrounding Aleppo, the country's largest city that has been divided between government forces and opposition fighters.
The growing siege of the city -- which had a prewar population of more than 2 million people -- has forced tens of thousands of civilians to flee north toward the Turkish border, about 40 kilometers away.
Merkel's comments came the same day that Human Rights Watch said the Russian-Syrian military operation has used cluster munitions in at least 14 attacks since January 26.
It said those attacks had killed 37 civilians -- including six women and nine children -- and wounded dozens of others.
The use of cluster bombs has been banned by 118 countries, but not by Russia or Syria.
Igor Konashenkov, a spokesman for the Russian military, said in December that there are no cluster munitions "at the Russian air base in Syria."
HRW says cluster munitions have been identified in photos and video taken at Russian's Hmeymim Air Base in Syria.
Nadim Houry, the deputy director of HRW's Middle East division, said that "any solution of the Syrian crisis needs to address ongoing indiscriminate attacks. A good place to start would be a commitment by Russia and Syria to stop using cluster munitions."
Turkish Prime Minister Ahmet Davutoglu said after meeting with Merkel on February 8 that some 30,000 Syrians from Aleppo are waiting at the border and would be allowed in "when necessary."
Davutoglu also blamed Russia for the new wave of refugees to Turkey, which has already taken in some 2.5 million Syrians since the civil war began in 2011.
At least 250,000 people have died in the conflict, and several million have fled their homes.
Davutoglu added that Turkey and Germany have agreed on a joint diplomatic initiative to end the Russian-Syrian offensive against Aleppo.
The EU has agreed to give Turkey 3 billion euros ($3.3 billion) in exchange for its efforts in stemming the tide of migrants coming to Europe.
Meanwhile, Davutoglu said Turkey and Germany will ask NATO at a February 11 meeting of the alliance’s defense ministers to become involved with "the flow of refugees from Syria."
"We will make a joint effort on the effective use of NATO's observation and monitoring mechanisms on the border and in the Aegean," he said.
More than 900,000 refugees and migrants crossed the Aegean Sea from Turkey to Greece last year, with hundreds of others drowning during the attempt.