Washington (CNN) US intelligence is monitoring a series of cargo flights from Iran into Syria that the US suspects may be carrying weapons systems into Syria for potential use by Bashar al-Assad's regime or Iranian forces, CNN has learned.

An administration official confirms to CNN that the flights took place and the US and Israel are both concerned the cargo could potentially include weapons that could eventually be used to threaten Israel.

While weapons shipments into Syria are not uncommon, these flights involving Iran have caught the attention of US intelligence because they occurred in the days after the April 13 US airstrikes on Assad regime targets. Rhetoric between Iran and Israel has also escalated in recent weeks over Tehran's involvement in areas of Syria that can be used to potentially launch missiles or aircraft that could target Israel.

Earlier this week, social media sites that track global air traffic recorded at least two flights by Syrian Air Force IL-76 cargo jets between Iran and Syria. The official said other flights, including at least one from an Iranian cargo jet, have also caught US attention.

Israel reportedly struck several targets inside Syria earlier this month including a T4 airbase in Homs province where Iranians had placed anti-aircraft missiles as well as unmanned aerial vehicles.

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