A Britain-based monitor said at least 10 people were killed when the regime bombed Douma neighbourhood in the capital. Three others died in an attack on Homs.
At least ten people were killed on Sunday when the Syrian regime dropped napalm on the rebel-held neighbourhood of Douma in Damascus, according to the Britain-based Syrian Observatory for Human Rights (SOHR). The monitor also said the regime bombed parts of Homs, killing three civilians.
SOHR said the regime carried out six air strikes against Douma during the napalm attack.
The latest air strikes came after a chain of suicide attacks on regime installations killed 42 people, including a senior intelligence officer.
UN Envoy to Syria Staffan de Mistura said the attack on Homs was a deliberate attempt to wreck ongoing Geneva peace talks.
FSA and regime forces clash
Also threatening the Geneva talks were clashes on Sunday between Turkey-backed Free Syrian Army (FSA) fighters and regime forces near al-Bab, captured last week from Daesh in northern Syria.
It was the second such confrontation in recent weeks. The FSA said the clashes took place south of al-Bab near the town of Tadef, which regime forces took from Daesh last week. There was no comment from the regime military.
The opposition Turkey-backed FSA and the Syrian regime are fighting Daesh in separate campaigns in the region north of Aleppo. Russia, which backs Bashar al-Assad's regime, intervened to prevent a similar conflict earlier in February.
The clashes between the FSA and regime forces were a focus of talks earlier this year in the Kazakh capital Astana, intended to prevent such incidents.
Assad's opponent Turkey and Assad's allies Russia and Iran reaffirmed a shaky ceasefire between the opposition and regime forces, during the first round of talks in January.
Russian President Vladimir Putin on Monday said the ceasefire and Astana talks helped jumpstart the UN-led Geneva talks.
"A mechanism to control the ceasefire has been created, which is the most important thing," Putin said on a visit to the Kazakh capital.
Both sides have accused the other of repeated violations of the ceasefire, as each continues its battle against Daesh, which is excluded from the Astana and Geneva talks.
Syria's main opposition group has accused the regime delegation of "stalling" the Geneva talks, which have not touched on the conflict's key issue for the opposition, which is political transition.
The High Negotiations Committee (HNC) made the charge after the Syrian regime's chief negotiator Bashar al-Jaafari said any opposition delegates who refused to condemn the suicide attacks on Homs were "accomplices of terrorism." The opposition later condemned the assaults.
"Jaafari is stalling. They don't want to start the political transition," HNC spokesman Salem al-Meslet said.
TRT World's Sarah Firth who is in Geneva spoke with Mohammad Alloush, a member of the opposition delegation. Alloush told her that "Choosing Bashar al-Jafaari to be the lead negotiator is a message from the regime to the world, and to the revolution. Because he doesn't want a solution."