Russia's Defense Ministry said one of its fighter jets crashed off the coast of Syria Thursday morning and that both pilots aboard were killed.

State news agency Tass cited the ministry as saying the Su-30 crashed while climbing after takeoff from the Russian air base at Hemeimeem in Syria.

Fall of a Russian plane in the sea off the port city in Syria

The ministry said the plane did not come under fire and that preliminary information indicates the crash could have been caused by a bird being sucked into one of the plane's engines.

>> Russia's covert mission in Syria uncovered >>

Russian President Vladimir Putin is a main ally of Syrian President Bashar Assad and has bases in the coastal areas of Syria, a stronghold of Assad.

According to reports in the Russian media last week, the Kremlin is planning to give Syria its advanced S-300 air defense system. The S-300 has become almost a byword over the last decade for a strategic advantage, also sought by Iran to counter Israel’s dominance in the air.

For years, Israel has lobbied the Kremlin not to supply the system to the Syrian regime. In an interview last week, Defense Minister Avigdor Lieberman sent a message to the Kremlin: “One thing should be clear – If someone fires on our planes, we will destroy them.”