A Russian naval intelligence ship sank Thursday after colliding with a merchant freighter in foggy conditions on the Black Sea near Istanbul, the Turkish coast guard said. All 78 crew members on the Russian vessel were rescued.

The crew of the freighter Youzarsif H, a Togo-flagged ship traveling from Romania to Jordan with a cargo of 8,800 sheep, was unharmed, and the ship suffered slight damage to its bow, according to local media reports. 

In Moscow, Russia’s Defense Ministry issued a statement confirming that the vessel, the Liman, went down after the collision tore a hole in the hull below the waterline.

Russian officials did not immediately provide any information about the Liman’s mission. The Russian state-run Sputnik news agency reported in 2016 that the Liman had been deployed in the Black Sea to monitor the Sea Breeze naval exercises involving Ukraine and several NATO countries, including the United States. Russian officials had complained that the exercises were a provocation.

Members of the Turkish coast guard help Russian sailors. (Turkish Armed Forces General Staff Press Office/European Pressphoto Agency)

Turkish Prime Minister Binali Yildirim called Russian Prime Minister Dmitry Medvedev to express “sadness,” Turkey’s semiofficial Anadolu news agency reported. 

 Russia and Turkey have developed increasingly warm ties over the past year, putting aside bitter differences over the war in Syria to cooperate on brokering a political solution to the conflict. The relationship reached a low point in 2015, when Turkey shot down a Russian warplane that Ankara said had crossed the Syrian border and entered Turkish airspace.

The collision Thursday occurred about 20 miles northwest of the Bosporus, one of the world’s busiest waterways, which connects the Black Sea to the shipping lanes leading to the Mediterranean.

At the time of the accident, the Bosporus was closed because of poor visibility, the Reuters news agency reported, citing the shipping agency GAC.

The Liman had also previously been deployed for three months to the Mediterranean near Syria, where Russia is in the second year of an intervention backing President Bashar al-Assad against a wide array of rebel groups, including Islamist fighters and others with U.S. backing.

Ship spotters in the Bosporus photographed the ship traversing the strait near Istanbul under heavy snow in January.

A member of the Turkish coast guard, left, helps a Russian sailor. (Turkish Armed Forces General Staff Press Office/European Pressphoto Agency)

It is not clear whether the ship was headed toward Syria on Thursday.

 The Liman was built as a hydrographic survey vessel in the Gdansk shipyards in Poland in 1970 and was converted for military service in 1989, shortly before the fall of the Soviet Union. The ship is outfitted to capture electronic-signals intelligence using an array of Soviet and Russian-made sensors for which the ship was retrofitted.

Roth reported from Moscow.