BEIJING, April 20 (Reuters) - Russia's coal shipments to China fell 21% in March dragged down by sanctions and import tariffs, customs data showed on Saturday.

China's coal shipments from Russia fell to 6.92 million metric tons in March, its General Administration of Customs said.

The shipments of Russian coal to China, which began to surge in 2022 as Western nations cut off trade with Moscow over the war in Ukraine, have been hit by recent U.S. sanctions on top exporters Suek and Michel and China's reinstated import tariffs of 3-6% this year, forcing exporters to cut prices.

China's overall coal imports in March were flat with last year due to oversupply and low domestic prices, with many buyers only taking imported coal they had already purchased under long-term contracts, market sources said.

Indonesia, which sells much of its coal to China under annual supply contracts, remained overwhelmingly the biggest supplier to China during the month. Shipments fell 9.9% to 19.8 million tons.

Imports from Mongolia, mostly of coking coal used for steelmaking, rose 11.9% from a year earlier, supported by improved overland transportation logistics.

Mongolian exporters are also benefiting from lower production by China's coking coal producing hub of Shanxi, which is increasing safety oversight following a rise in deadly accidents and plans to cut output by around 4% this year.

China's coal imports from Australia rose 130% in the month, boosted by Australia's tariff-free status and by a low base effect.

Chinese imports of Australian coal were still recovering in March 2023 following the end of an unofficial ban. (Reporting by Colleen Howe, Mei Mei Chu and Amy Lv; editing by Miral Fahmy and Shri Navaratnam)