Moscow is sending three large landing ships with marines aboard to a Russian naval facility in the Syrian port of Tartus, Russian news agencies quoted a source in the general staff as saying on Friday.

The source said each ship would have up to 120 marines on board and that the vessels, already in the Mediterranean, would arrive in Tartus by the end of this week or early next week.

The source said the ships’ mission was to replenish supplies at the small Russian maintenance and repair facility, manned by fewer than 100 personnel, according to analysts.

Russia had earlier said it was preparing to send marines to Syria in case it needed to protect personnel and remove equipment from the naval maintenance facility.

Syria is Moscow’s firmest foothold in the Middle East and bought $ 1 billion worth of weapons from Russia last year, or about 8 per cent of total Russian arms exports.

Tartus is the Russian navy’s only permanent warm water port outside the former Soviet Union.

The source in the Russian General Staff said the three ships would be joined by three other ships from the Russian Navy’s Black Sea and Northern Sea fleets.

The potential loss of Tartus would be a strategic blow to Russia, according to what the Interfax news agency described as a military-diplomatic source.

“Tartus is of extreme military-strategic importance for the Russian Navy, as the backup for the task forces in the Mediterranean. Therefore, its loss would entail deep negative consequences and the actual loss of influence in this key region,” Interfax quoted the source as saying.