If confirmed, it would be the first attack on Syrian territory since US President Donald Trump on Monday recognised Golan Heights -- seized from Syria in the 1967 Six-Day War -- as Israeli territory, a move which breaks with decades of international consensus.

"Army air defences repels an Israeli air aggression that targeted a number of industrial sites in Sheikh Najjar industrial zone, north-east of Aleppo, and downed a number of the hostile missiles," Syria's official SANA news agency said, citing an unnamed military source.

War monitor the Syrian Observatory for Human Rights said the Israeli bombardment hit "ammunition stores belonging to Iranian forces and allied groups, and caused huge explosions."

It added that at least four people, believed to be warehouse guards, were killed.

A number of residents of Aleppo told AFP that the attack led to a power cut in the whole city.

Israel has carried out hundreds of air strikes in Syria in the past few years targeting positions held by its main enemy Iran and its Lebanese ally Hezbollah, with the goal of stopping Iran from entrenching itself militarily in the war-torn country.

Iran is a major supporter of President Bashar al-Assad in the Syrian civil war.

In January Israel hit a number of Iranian installations in the country, hours after intercepting a rocket fired from Syrian territory.

The Observatory said 21 people, mostly Iranians, were killed in those attacks.

In May 2018, Israeli strikes killed 27 pro-regime fighters including 11 Iranians in strikes on dozens of Iranian targets inside Syria.