MOSCOW/BEIRUT (Reuters) - Russia shipped a diesel cargo to Syria onboard a tanker under U.S. sanctions, the first known such direct supply to the Middle Eastern country in more than a decade, LSEG data showed.

The final destination of the cargo is unclear. Russia has two main military installations in Syria: an air base in Hmeimim and a naval base in Tartous, integral to Russia's military reach in the Middle East and Africa.

Russia's control over the bases is under threat following the sudden fall of Bashar al-Assad last year. Moscow has said it wanted to keep its hold over them.

According to LSEG data, the Barbados-flagged vessel Prosperity (previously known as Gabon-flagged NS Pride) was loaded with about 37,000 metric tons of ultra-low sulphur diesel at the Russian Baltic port of Primorsk on February 8.

The tanker, managed by the Dubai-based Fornax Ship Management, is anchored near the Syrian port of Banias, LSEG shipping data shows. Fornax itself is also under the U.S. sanctions. The company was not immediately available for comment.

U.S. sanctions on Russia since the start of the 2022 invasion of Ukraine have included measures aimed at limiting revenues from the country's huge oil and gas industry and weakening its ability to fund the military efforts.

The United States on January 10 added the Prosperity to the list of sanctioned vessels, which includes some 180 tankers, involved in the export of Russian oil products following its war in Ukraine. The EU and the UK followed suit on February 24.

Violations of the U.S. sanctions programs may result in civil and, in some cases, criminal penalties.

In one such case, U.S. Department of the Treasury's Office of Foreign Assets Control (OFAC) announced last year a settlement of $7.45 million with the State Street Bank for "apparent violations" of the Russia and Ukraine-related sanctions.

At the same time, the U.S. issued a six-month waiver to its Syria sanctions, focused on the energy sector and financial transfers to Syrian governing authorities.

Syrian oil ministry officials did not immediately respond to text messages seeking comment. Russia's energy ministry declined to comment.

This is the first direct diesel shipment from Russia to Syria since at least 2013, according to LSEG data.

Syria also issued an import tender for 20,000 tons of LPG and was seeking to import oil as no crude shipments have arrived from Iran, its key supplier, since November, according to data from shipping analytics firm Kpler.

Syria has two oil refineries, located in Homs and Banias, which ceased operating after Assad's fall.