Syria said Israeli air strikes hit a military facility in the country's west on Thursday, killing two people at a site where the regime has been accused of developing chemical weapons.

The site near the Syrian town of Masyaf, between the central city of Hama and a port used by the Russian navy, includes a training camp and a branch of the Scientific Studies and Research Center (SSRC).

The United States has accused the SSRC of helping to develop the sarin gas used in an attack on the Syrian town of Khan Sheikhun in April that killed dozens.

President Bashar al-Assad's government has blasted such accusations as "fabrications," and Syria's army on Thursday did not mention the SSRC in its statement on the Israeli strikes.

"Israeli warplanes at 2:42am today fired a number of missiles from Lebanese air space, targeting one of our military positions near Masyaf, which led to material damage and the deaths of two members of the site," the statement said.

"Syria's army warns of the serious repercussions of such acts of aggression on the security and stability of the region," it added.

Since Syria's conflict erupted in 2011, Israel has conducted several air strikes on the war-ravaged country against government forces and allied fighters from Lebanese movement Hezbollah.

The British-based Syrian Observatory for Human Rights monitoring group said Hezbollah fighters and Iranian military personnel were known to use the site at Masyaf.

"There are Iranian experts using the research centre there. Hezbollah also uses the facility," said Observatory head Rami Abdel Rahman.

"The research centre was definitely damaged in the strikes. There is huge fire emanating from a weapons warehouse where missiles were being stored," he added.

- 'Produces chemical weapons' -

Israel officials declined to comment on the raids on Thursday.

Former military intelligence head Amos Yadlin said the site targeted on Thursday "produces the chemical weapons and barrel bombs that have killed thousands of Syrian civilians."

He stopped short of saying Israel had carried out the raids, but said that if it did, they would show "Israel intends to enforce its redlines despite the fact that the great powers are ignoring them."

On Wednesday, United Nations war crimes investigators announced they had an "extensive body of information" indicating Syrian warplanes were behind the deadly April 4 attack on Khan Sheikhun.

A fact-finding mission by the UN's chemical watchdog, the Organisation for the Prohibition of Chemical Weapons (OPCW), concluded earlier this year that sarin gas was used in the attack but did not assign blame.

The attack left at least 87 people dead and prompted the United States to launch a cruise missile strike on a Syrian military airport where it said the attack had originated.

Weeks later, the US sanctioned 271 Syrian chemists and other officials affiliated with the SSRC, which it said was behind the Syrian government's efforts to develop chemical weapons.

Syria's government claims it no longer possesses chemical weapons after a 2013 agreement under which it pledged to surrender its chemical arsenal.

But in 2016, a UN-led investigative body said the Syrian government was behind at leat three chemical attacks in northern Syria in the previous two years.