At least nine pro-regime hunters died in a suspected Israeli rocket attack at night in northern Syria, a monitor said Monday.
The Syrian state media had accused Israel of bombing a military position in the province of Aleppo on Sunday, which would be a rare Israeli attack in the war-torn country.
The Syrian human rights observatory, a war observer stationed in Britain, said the base was used by the Syrian regime, the arch rival of Iran.
"The Israeli missiles have attacked a center of the Iranian revolutionary guard near the military air base Neirab," said Rami Abdel Rahman, acting head of the observatory.
He said that the killers contained at least six Syrians but could not name the nationalities of the remaining combatants.
The location is a logistic hub used for supplying equipment and food for pro-regime troops fighting on nearby fronts, but who did not store weapons, said Abdel Rahman.
Tehran has deployed the armed forces to support the efforts of Syrian President Bashar al-Assad to crush a seven-year rebellion against his rule.
Assad said the armed forces were advisors, but denied the presence of Iranian hunters on Syrian territory.
At the end of Sunday, the SANA news agency said Israeli missiles had landed close to a strategic air base, but said it had no casualties.
"The Zionist enemy … erected his missiles at one of our military positions north of Neirab's military air base, but the damage was material," he said, referring to a military source.
The Israeli army refused to comment on the reports.
The attack is the third suspected Israeli attack on Syria alone this month.
Damascus accused his archenemy of taking a military position in Central Syria on July 8, and Israel said it had reached three military posts in the country a few days later.
Alleged Israeli attacks mostly struck army camps near Damascus and the central provinces of Homs and Hama, but were rarely as far north as Aleppo.
Israel has repeatedly warned that it will tolerate an entrenched presence of its archenemy Iran in neighboring Syria.
In May it launched an unprecedented strike wave against dozens of Iranian military targets in Syria.
Israel has been in focus for the past few weeks, while the Assad forces are fighting to recapture parts of southern Syria that border the Golan Heights annexed by Israel.
After taking the majority of Daraa's main province, government troops launch an offensive in the neighboring province of Quneitra, which is largely owned by the rebels.
They started heavy bombing in the area on Sunday morning and the air strikes continued there on Monday, the observatory said.
The news agency SANA said that the rocket attack near the strategic air base in the province of Aleppo, much more likely than expected, the Israeli attacks take place.