MOSCOW, April 19 (Reuters) - Russia's exports of liquefied petroleum gas (LPG) to China by rail, the main supply route, rose 51% in the first quarter from a year earlier to 72,300 metric tons, Reuters calculations based on data from industry sources showed.

Traders said that the main contributor to the increase was Irkutsk Oil Company (INK), which raised exports from its Ust-Kut gas processing plant.

Russia has been cranking up LPG exports to China, including by road in trucks, to offset a decline in supplies to the European Union, which adopted a twelfth package of sanctions against Russia in December, introducing a new LPG import ban, to top up wide-ranging trading restrictions.

Traders believe that Russia will continue to increase supplies of LPG, or propane and butane, to China thanks to available exporting infrastructure despite congested railways.

There is a room to increase exports further. China accounted for only 6% of last year's 3.6 million tons of Russian LPG exports via railway.

The Zabaikalsk-Manchuria border crossing is the main route for Russian LPG exports to China, with the Manzhouli Far East Gas terminal able to handle 1 million tons of LPG per year. (Reporting by Reuters; writing by Vladimir Soldatkin; Editing by Louise Heavens)