Explosions were heard in Damascus on Sunday night. According to local reports, the target is the al-Mezzeh airbase, which has been hit by several alleged Israeli airstrikes in the past.
This is a developing story.
According to the Syrian Al-Marsad organization for human rights, Thursday's attack on the Dabaa military airport in central Syria was aimed at Hezbollah members and militias.
The Syrian army and its allies have for years employed siege and bombardment tactics to force rebels to surrender their enclaves and agree to be transferred to opposition territory in northern Syria.
Syria, Iran and Russia all said Israel was responsible for carrying out the attack at the T-4 air base near Homs.
Israel has not confirmed or denied mounting the raid, but has repeatedly refused to accept Iranian military presence in Syria.
An Israeli military spokesman said he had no immediate comment.
A string of bombings have struck cities under government control in Syria this year, including the capital Damascus.
The Syrian Observatory said on Friday around 70 rockets had fallen in 24 hours on Eastern Ghouta in the heaviest bombing since the de-escalation zone was declared.
ISIS falls back to the advancing Syrian and Iraqi armies, but attacks on high ranking Syrian officers show the Islamic State is far from surrendering.