The drills are taking place two days after US President Donald Trump said he had ordered two nuclear submarines to be positioned in "the appropriate regions" in response to remarks by former Russian president Dmitry Medvedev.
However, they were scheduled well before Trump's action.
Interfax news agency quoted the Pacific Fleet as saying Russian and Chinese vessels were moving in a joint detachment including a large Russian anti-submarine ship and two Chinese destroyers.
It said diesel-electric submarines from the two countries were also involved, as well as a Chinese submarine rescue ship.
The manoeuvres are part of exercises titled "Maritime Interaction-2025" which are scheduled to end on Tuesday.
Interfax said Russian and Chinese sailors would conduct artillery firing, practise anti-submarine and air defence missions, and improve joint search and rescue operations at sea.
Russia and China, which signed a "no-limits" strategic partnership shortly before Russia went to war in Ukraine in 2022, conduct regular military exercises to rehearse co-ordination between their armed forces and send a deterrent signal to adversaries.
Trump said his submarine order on Friday was made in response to what he called "highly provocative" remarks by Russia's Medvedev about the risk of war between the nuclear-armed adversaries.
Russia and the United States have by far the biggest nuclear arsenals in the world.
It is extremely rare for either country to discuss the deployment and location of its nuclear submarines.
Trump's comments came at a time of mounting tension with Moscow as he grows frustrated at the lack of progress towards ending the Ukraine war.
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