Satellite photos published Thursday purported to show the establishment of an Iranian surface-to-surface missile factory in Syria, raising fresh concerns over the extent of the two countries’ military cooperation on Israel’s northern border.

The photos, which were taken by ImageSat International and published by Channel 10 news, were said to show a facility outside Wadi Jahannam in northwest Syria resembling Iran’s Parchin facility, which has been linked to the Islamic Republic’s ballistic missile and nuclear programs.

Beyond noting an apparent surge in construction work at the site and the building’s seeming similarity to Parchin, Channel 10 did not say how it was identified as a missile factory.

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Unlike other Iranian facilities in Syria that have been targeted in Israeli airstrikes, the report said the site was likely spared due to its close proximity to a Russian S-400 ant-aircraft battery, which is considered to be one of the most advanced air defense systems in the world.

In July, Israeli jets reportedly targeted a missile production facility in nearby Masyaf, where a leading Syrian chemical weapons and missile scientist was killed earlier this month in a car bombing attributed to Israel.

According to a New York Times report, Israel believed that Dr. Aziz Asbar was leading a classified weapons development program called Sector 4 at the Syrian Scientific Studies and Research Center, and was busy rebuilding an underground weapons factory to replace the one said destroyed by Israel.

Israel did not comment on its alleged involvement in the July airstrike on the facility, but Prime Minister Benjamin Netanyahu said in a statement following the raid that Israel “will not stop taking action in Syria against Iran’s attempts to establish a military presence there.”

Iran has been one of the top military backers of Syrian President Bashar Assad’s regime in the over sever-year-long civil war in the country, as has been its Lebanese proxy, the Hezbollah terror group.

Both Israel and the United States have called for the removal of all Iranian-backed forces from Syria. Russia, which like Iran is fighting on behalf of Assad, has expressed support for this goal but said it can’t force Iranian forces out of the country.

Iran for its part has vowed to remain in Syria, and earlier this week the two countries signed a defense agreement during a visit by Iranian Defense Minister Amir Hatami to Damascus.

Hatami said the pact would include the rebuilding of Syria’s military and defense programs.

Netanyahu this week reiterated that Israel will continue to take action against Iran’s military entrenchment in Syria, and issued an emphatic warning against those who call for Israel’s annihilation, such as the Islamic Republic.

“Whoever threatens us with destruction puts himself in similar danger, and in any case will not achieve his goal,” Netanyahu said during a ceremony at the nuclear research facility in Dimona.