At least nine pro-regime fighters died in a suspected Israeli rocket attack overnight in northern Syria, a monitor said Monday.
The Syrian state media had accused Israel of bombing a military position in Aleppo province on Sunday, which would be a rare Israeli strike in the war-torn country.
The Syrian Observatory for Human Rights, a war observer stationed in Britain, said the base was being used by the Syrian regime, the arch rival of Iran.
"The Israeli rockets have attacked a center of the Iranian Revolutionary Guard near the military airbase Neirab," said Observatory Chief Rami Abdel Rahman.
He said that the killers contained at least six Syrians, but could not state the nationalities of the remaining fighters.
The location is a logistics hub used to provide equipment and food for pro-regime forces fighting on near fronts, but it stored no weapons, Abdel Rahman said.
Tehran has deployed armed forces to support the efforts of Syrian President Bashar al-Assad to crush a seven-year uprising against his rule.
Assad said that the armed forces were consultants, but denied the presence of Iranian fighters on Syrian territory.
On late Sunday, the state news agency SANA said that Israeli rockets had been hit near a strategic air base, but said it had no casualties.
"The Zionist Enemy … aimed its missiles at one of our military positions north of the military airbase of Neirab, but the damage was material," it said, citing a military source.
The Israeli military refused to comment on the reports.
The attack is the third suspected Israeli attack on Syria this month alone.
Damascus accused his archenemy of taking military position in Central Syria on July 8, and Israel said it had reached three military posts in the country a few days later.
Suspected Israeli attacks usually hit army positions 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 on high alert in recent weeks as Assad's forces fight to recapture parts of southern Syria bordering on the Golan Heights annexed by Israel.
After taking the majority of the main province of Daraa, the government forces are launching an offensive in the neighboring province of Quneitra, which is largely rebel-owned.
They began Sunday morning with heavy bombing of the area and on Monday the air raids continued there, the observatory said.
The state news agency SANA said the rocket attack near a strategic air base in the province of Aleppo, far north than suspected Israeli attacks usually occur