Syrian government air strikes killed 15 civilians on Tuesday, as militant groups were reported to have launched a series of three attacks on the regime's troops.
At least 12 people were killed in a midnight strike on a market in the militant-held town of Maarat Al Numan in Idlib province, the UK-based Syrian Observatory for Human Rights said. Three others were killed in two separate strikes on Wednesday, it said.
Syrian government forces repelled three large attacks in Idlib, Russia's Ministry of Defence said on Wednesday through its state-backed news agencies.
Some 500 militants from Hayat Tahrir Al Sham – who are a coalition of smaller groups, the largest of which is the Nusra Front, a former Al Qaeda affiliate – supported by seven tanks and 30 armed pickup trucks launched the attacks they said.
The defence ministry said 150 militants were killed and three tanks and 24 of the trucks destroyed in the attack. But the Syrian Observatory for Human Rights placed the number at 52.
Fighting took place in an internationally agreed buffer zone, brokered between Turkey and Russia in September last year. The zone was agreed to avoid a slaughter from a government offensive in the region, protecting the lives of three million residents.
Militants launched a failed missile attack on Russia's Hmeymim air base, the Russian ministry said.
Syrian President Bashar Al Assad's government, with the support of Russia, has upped its bombardment of Idlib after militant coalition HTS took control of the area in January.
On Tuesday, the US State Department was assessing whether the Syrian government had used chemical weapons on Sunday during its offensive in Idlib.
HTS accused government forces of launching a chlorine gas attack on its fighters in the northern mountains of Latakia – the only part of the coastal province that is not firmly in the hands of the government.
The French foreign ministry said on Wednesday the accusations must be looked into.
"We have noted with a degree of alarm these allegations, which need to be looked into," the foreign ministry said in an online press briefing.
But the Observatory said on Wednesday it had no evidence to suggest the Syrian army had carried out a new chemical attack.
"We have no proof at all of the attack," Observatory chief Rami Abdul Rahman said.
"We have not documented any chemical attack in the mountains of Latakia," he told AFP.
