Government warplanes also began dropping leaflets over Idlib demanding residents 'comply' or face consequences
Syrian air defences reportedly engaged an "enemy target" near the border with Lebanon west of Damascus overnight Saturday, a day after it struck rebel areas and killed dozens of civilians in northern Syria on Friday.
"Our air defences confronted an enemy target that penetrated airspace above the area of Deir al-Ashair in the Damascus countryside," state news agency SANA said.
The Syrian Observatory for Human Rights confirmed air defences had launched missiles, but said it was unclear what they were targeting or whether there was any target at all.
The UK-based war monitor said Lebanese group Hezbollah, which has been backing the Damascus government in Syria's seven-year civil war, was present in the area.
Israel has carried out numerous raids in Syria in recent years, targeting government forces, Hezbollah and Iran, another ally of Damascus.
Last week, SANA said Syrian air defences confronted another "enemy attack" west of Damascus. The Observatory, which relies on sources inside Syria for its information, said it was unable to determine who was responsible.
Last month, Syria accused Israel of bombing a military post in the northern province of Aleppo, where the Observatory reported at least nine pro-regime fighters died.
Leaflet drops over Idlib
This latest escalation comes after Syrian government planes killed 30 civilians across northern Syria on Friday, in some of the fiercest shelling of rebel-held areas in months.
The air strikes and barrel bombs targeted the key opposition-held province of Idlib in Syria's northwest and a rebel town in the adjacent province of Aleppo.
Idlib is the largest chunk of territory still in rebel hands, and President Bashar al-Assad has warned it would be his next target.
The province's southwest was shelled heavily on Thursday and the bombing the next day "moved further east," leaving 11 civilians dead, according to the Syrian Observatory for Human Rights.
"Air strikes by Russian warplanes and barrel bombs from Syrian helicopters hit southern parts of Idlib province today in very heavy shelling," Observatory head Rami Abdel Rahman said on Friday.
Government planes reportedly dropped leaflets over northern Syria, urging residents to surrender, as it prepares an all-out assault on Idlib.
Local journalists and activists reported that leaflets dropped on rural areas called on residents "must pursue reconciliation" and give the government control of Idlib.
Syrian man holds a leaflet dropped over the rebel-held town of Saraqeb in northern Syria (AFP)
"The war is about to end. It's time to stop the war and the bloodshed," read one leaflet.
Earlier this year, senior Arab officials in Amman, Jordan, and Beirut described conditions in Idlib as a "well-constructed kill box" as refugees continue to pour into the last remaining rebel-held areas of Idlib and Hama.
Idlib remains the largest populated area of Syria out of the government's control.
In recent years, tens of thousands of fighters and civilians have fled there from parts of the country which the army has recaptured with the help of Russia and Iran.
Since Russia intervened on its side in 2015, the Syrian government has regained control of around half of the country.
More than 350,000 people have been killed in Syria's war since it started in 2011 with the brutal repression of anti-government protests.