BEIJING, May 20 (Reuters) - Coal imports from China's largest supplier Indonesia tumbled 20% to 14.286 million tons in April, customs data showed on Tuesday, as Chinese buyers rejected a push by Jakarta to use its government-set benchmark in international sales, in a bid to increase royalties.

Indonesia began using the new government-set price, known as HBA and previously used only to calculate royalties, on March 1 to exert more national control over the value of both domestic and export transactions for the fuel commodity, but traders complain the index is opaque and more expensive.

Also weighing on Indonesian imports were lower prices for domestic coal in China, which dragged down overall coal imports by 16% year-on-year in April.

Domestic prices are at four-year lows, cutting into profit for imported coal.

China's coal imports from other top suppliers also fell last month. Russian shipments fell 13% in April from the same month last year to 7.397 million metric tons, the data showed.

Moscow is planning to support its coal industry, hit by Western sanctions, with discounts on rail transportation rates and guaranteed exports, according to a letter seen by Reuters and reports from coal-producing regions, which could support shipments to neighbouring China going forward.

Imports from Mongolia, mostly of coking coal, dipped 3% to 7.014 million tons last month. Imports from Australia also declined 3% in the month to 6.97 million tons.

Below are the details of imports from key suppliers with volume in metric tons: