Israel struck Syrian regime positions in the Tall al-Hara region in the Daraa province, south of Damascus, said the Syrian Observatory for Human Rights.
The “probably Israeli” attacks also targeted two areas in the neighboring province of Quneitra, it added.
"The regime's anti-aircraft defense has been activated to counter the attack," director of the Britain-based Observatory Rami Abdel Rahman said.
"Some missiles have been shot down, others have hit their target."
The Observatory reported "loss of life" without giving further details.
Syria's state news agency SANA said the Israeli strike targeted Syrian military positions in Tall al-Hara.
Israel has carried out hundreds of air strikes in Syria since the beginning of its conflict in 2011, targeting forces loyal to regime leader Bashar Assad and his allies Iran and Hezbollah.
The conflict has killed more than 370,000 people and drawn in world powers since it started with the brutal repression of anti-regime protests.
Israeli strikes have previously targeted Tall al-Hara where Hezbollah has installed a radar system and the regime has erected anti-aircraft batteries, according to the Observatory.
At the end of June, six civilians and nine pro-regime fighters were killed in Israeli strikes near Damascus and in the central province of Homs, it added.
Israel says it is determined to prevent its arch-foe Iran from entrenching itself militarily in Syria, where Tehran backs Assad.
Israel insists that it has the right to continue to target positions held by Iran and its Lebanese ally Hezbollah out of self-defense.
Tall al-Hara is a strategically located area in southern Daraa province overlooking the Israeli-held Golan Heights. It was for many years a major Russian military radar outpost until opposition factions took it over in 2014 before it was again recaptured by the regime last year.
