Israel made an air attack on Syria this month that targeted advanced anti-ship cruise missiles sold to the Syrian government by Russia, US officials said.

The officials, who declined to be identified, said the attack occurred on July 5 near Latakia, Syria’s principal port city. The target was a type of missile called the Yakhont, the officials said.

A spokesman for the Israeli Prime Minister, Mark Regev, declined to comment on the strike, as did George Little, the Pentagon spokesman.

The Russian-made weapon has been a particular worry for the Pentagon because it expanded Syria’s ability to threaten Western ships that could be used to transport supplies to the Syrian opposition, enforce a shipping embargo or support a possible no-fly zone.

The missile also represented a threat to Israel’s naval forces and concerns had been raised that it might be provided to Hezbollah, the Lebanese militia that has joined the war, siding with the Syrian government.

The attack against the missiles came to light after Syrian rebels said they were not responsible for large explosions at Latakia on July 5, and that a missile warehouse had been hit. American officials did not provide details on the extent of the damage or the number of missiles struck.

Israeli officials have said they would not take sides in the civil war in Syria but they have made it clear that Israel is prepared to make air strikes to prevent sophisticated weapons from being diverted to Hezbollah.

The strike near Latakia, first reported by CNN, was the third known Israeli air attack directed at shipments of advanced weapons sent to Syria this year.

While the Obama administration has been cautious about getting involved militarily in the Syria crisis, the Israeli attack this month underscored how the conflict has continued to draw in outside powers. Iran has been ferrying weapons to Damascus on flights that pass through Iraq’s airspace and has sent members of its paramilitary Quds Force to help the government of President Bashar al-Assad.

Thousands of Hezbollah fighters have gone to Syria to fight with Syrian government forces, as have Iraqi Shiite fighters, with the strong encouragement of Iran. Russia has continued to supply arms to the Syrian government.

Qatar and Saudi Arabia have provided weapons to the rebels. The US has provided ”non-lethal” military aid, including food and medical kits, and pledged to expand support to the armed wing of the opposition.

In late January, Israel made an air strike against a weapons convoy that carried Russian-made SA-17 surface-to-air missiles, which Israeli officials said they believed were to be provided to Hezbollah.

During a visit to an army base last week, Israel’s Defence Minister, Moshe Yaalon, restated Israel’s approach to the Syrian conflict: that it would not get involved except to stop weapons transfers.