Russian military forces deployed in Crimea have received advanced missile systems as part of Moscow’s plans to protect the region’s airspace, a report said Wednesday, citing a Black Sea military source.

The military source from Russia’s Black Sea Fleet told Russian news agency RIA Novosti that the country’s military in the Crimean peninsula has received new S-300PMU surface-to-air missile systems, providing a significant boost to Russian military capabilities in the region. According to the report, the S-300PMU systems arrived in Crimea in November, but details about the exact number of the missiles and the area of their deployment are still unknown.

“With the appearance of the S-300PMU complexes, it can be said with confidence that a full-fledged missile shield has been created on the peninsula that is capable of providing for the security of the Black Sea Fleet [from threats] from the air,” the source told RIA Novosti.

The S-300PMU missile system, with the NATO reporting name “Grumble,” was introduced in 1992 for the export market. The missile, which utilizes the Big Bird surveillance radar, can hit targets at a maximum range of 124 miles. The missile family, which was first deployed by the Soviet Union in 1979, reportedly has the reputation of being one of the best anti-aircraft missile systems in the world.

The latest report follows last week’s reports stating that the Russian Air Force had sent more than a dozen advanced warplanes, including 10 Sukhoi Su-27SM fighters and four Su-30 fighter-bombers, to Belbek, an air base on the outskirts of the Crimean city of Sevastopol. Russian forces seized Belbek in March.