The reports feature satellite images showing a site under construction in northwest Syria near the Mediterranean coastal town of Baniyas that purportedly could be used to produce and store the weapons, RFE/RL reported.
Israeli Prime Minister Benjamin Netanyahu has warned recently that Iran is augmenting its presence in Syria as the six-year civil war there has turned more favorably toward Tehran's ally, Syrian President Bashar al-Assad.
"Our policy is clear: We vehemently oppose the military buildup by Iran and its proxies, primarily Hizballah, in Syria and we will do whatever it takes to protect Israel's security," Netanyahu said in a speech last week.
Iran, which has not officially commented on the Israeli reports, is Israel's avowed enemy and for years has provided Assad with military advisers and militias to wage his civil war.
An Israeli Channel 2 television news report showed images it said were taken by an Israeli satellite showing a weapons-factory construction site and indications that explosives would be stored there.
The report compared images of buildings it said were of a rocket factory near Tehran to structures at the Syrian site and said there was a strong resemblance between them.
The Times of Israel reported that the missile factory is being built in a bastion of support for the embattled Assad government and could be used for the production and underground storage of Scud missiles capable of striking Israel.
Read alsoIran could quit nuclear deal in 'hours' if new U.S. sanctions imposed – mediaIt said dirt berms could be seen around the factory buildings in satellite photos to protect them from attack. It added that the same site can viewed by anyone on Google maps.
The Times said Iran was also helping Hizballah build subterranean factories in Lebanon to make Fateh-110 medium-range missiles that would be able to reach most parts of Israel.
Israeli Defense Minister Avidgor Liberman last month publicly warned Hizballah and Iran against building the weapons factories.
"We are fully aware" of the rocket factories, Liberman told military correspondents at a briefing in Tel Aviv. "We know what needs to be done.... We won't ignore the establishment of Iranian weapons factories in Lebanon."
The alarms raised by Israel about Iran establishing a long-term military presence in Syria and Lebanon have been heeded by the administration of U.S. President Donald Trump, which has said this year it will not accept any peace settlement in Syria that allows Iran to maintain a military presence in the country.
U.S. news reports say Israeli intelligence officials will discuss the situation in Syria and Lebanon with U.S. counterparts in a visit to Washington this week.