Syrian Observatory for Human Rights says the overnight raids targeted Yarmouk Palestinian refugee camp and a small enclave south of the capital Damascus under the control of militants.
The Syrian regime forces bombarded militants in the last area outside regime control near Damascus overnight, a war monitor said on Friday, as Bashar al Assad accelerated his push to retake remaining enclaves.
Air strikes and shelling hit the Yarmouk Palestinian refugee camp and Al Hajar al Aswad area, part of a small enclave divided between warring militants and other rebels south of the capital, the Britain-based Syrian Observatory for Human Rights (SOHR) said.
Assad is accelerating his campaign to retake the remaining enclaves as his forces encircle around Syria, which would leave rebels with only their two major strongholds in the northwest and southwest.
Western countries launched their first co-ordinated action against Assad last week (April 14) to punish him for a suspected gas attack they say killed scores of people during an advance that captured the town of Ghouta near the capital.
But the single volley of air strikes, hitting three targets far from any front line, had no effect on the wider war which has killed nearly 500,000 people and made more than half of Syrians homeless.
Investigators still waiting to enter Douma
International inspectors from the Organisation for the Prohibition of Chemical Weapons (OPCW) who arrived in Damascus nearly a week ago were still waiting early on Friday to visit the site of the suspected poison gas attack.
The Syrian regime and its ally Russia deny using chemical weapons in the assault on Douma.
The Western countries say the regime, which now controls the town, is keeping the inspectors out and may be tampering with evidence, both accusations which Damascus and Moscow deny.
More rebels pulling out
Rebels on Thursday began pulling out of Dumair, an enclave northeast of Damascus, under a surrender deal with the regime. Insurgents in another enclave nearby, Eastern Qalamoun, said they had also agreed to withdraw.
Thousands of civilians, including the fighters' families, are expected to leave with them for northern Syria before the areas come back under Assad's rule under deals similar to others carried out across the country as Syrian regime forces advance.
The UN has voiced concern that such "evacuations" involve the displacement of civilians under threat of reprisals or forced conscription, though the regime denies that.
"The UN expects further displacements in the near future to northern Syria from other locations controlled by non-regime armed groups where negotiations reportedly are happening," the world body said in a humanitarian note.
Conditions in the opposition-held pocket of northern Syria where the displaced will go are poor.
After the regime forces' recovery of eastern Ghouta this month in a ferocious battle that began in February, the surrender of Dumair and Qalamoun would leave only the pocket in south Damascus outside regime control in the area around the capital.
Yarmouk was the biggest camp for Palestinian refugees in Syria before the war.
Although most residents have fled, up to 12,000 remain there and in the neighbouring areas under militant or rebel control, said the UN agency that helps them.
Russia says no moral obligation to withhold S-300 from Assad
US military strikes on Syria last week removed any moral obligation Russia had to withhold S-300 anti-aircraft missile systems from its ally Syrian regime leader Bashar al Assad, Russian Foreign Minister Sergey Lavrov said on Friday, RIA state news agency reported.
Lavrov was also quoted as saying that, prior to the US strikes on Syrian targets, Russia had told US officials which areas of Syria represented "red lines" for Moscow, and the US military action did not cross those lines.
He said that he was convinced Russian President Vladimir Putin and US President Donald Trump would not allow an armed confrontation between their two countries.
Syria as a single country?
Meanwhile, Russia's Deputy Foreign Minister Sergei Ryabkov said on Friday Moscow did not know how the situation in Syria would evolve in terms of the country maintaining its territorial integrity, the Interfax news agency reported.
"We don't know how the situation is going to develop on the question of whether it is possible to keep Syria as a single country," the agency quoted Ryabkov as telling Germany's Deutsche Welle broadcaster.