Vietnam calls it the East Sea.

"In accordance with the 2019 plan of measures approved by Russia's Defense Ministry for developing ties with the armies of foreign states, the Pacific Fleet’s rescue vessel Igor Belousov will take part in the joint Russian-Vietnamese exercise for assisting the crew of a submarine in distress lying on the seabed," Russia's Pacific Fleet said in a release on Tuesday.

Igor Belousov is one of Russia's most modern submarine rescue ships, and was inducted into service in 2015. It is nearly 107 meters long and has a displacement of more than 5,000 tons and a crew of 96. It can accommodate 120 rescued people.

Vietnam operates six Kilo-class submarines built at the Admiralty Shipyard in Russia.

Vietnam recently sent its warships to Russia for a fleet review on the occasion of the 323rd anniversary of the Russian Navy.