(Reuters) – Russia has shipped a battery of S-300 anti-aircraft missiles from Syria to a Russian port near Crimea, according to an Israeli satellite imaging company, in an apparent attempt to bolster its air defenses in the war with Ukraine.

ImageSat International (ISI) captured images showing the presence of an S-300 anti-aircraft battery in Masyaf, Syria in April, and the empty site left on August 25 after the devices were shipped to the port of Tartus.

Separate photos showed battery components on a dock in Tartus between August 12-17. By August 20, she had left, and the ISI concluded that she had been transferred to a Russian ship, the Sparta 2, which had left Tartus for the Russian port of Tartus. Novorossiysk.

Data from Refinitiv Eikon show that Sparta II is currently in Novorossiysk, having reached through the Turkish Dardanelles Strait.

The Russian Defense Ministry declined to comment.

Russia has maintained a military presence in Syria since 2015, when it intervened in the civil war there on the side of Syrian President Bashar al-Assad.

If confirmed, the relocation would mark a major Russian move to bolster air defenses near the theater of war in Ukraine, where its forces have come under devastating attacks in recent weeks.

In one such incident, eight Russian fighter jets were destroyed this month in a series of explosions at an air base in Crimea. Ukraine refused to say whether and how it carried out the attacks.

ISI images showed the transfer of the radar component of the S-300 battery separately from the same Masyaf base to the Hmeimim air base on the Syrian coast north of Tartus.

The company’s analysts said they estimated the radar’s size and weight made it unsuitable for shipping by sea, and might require an Ilyushin 76 airlift from Hmeimim to Russia.

(Reporting by Mark Trevelyan, Editing by William MacLean)