MOSCOW, July 10 (Reuters) - Russia cranked up liquefied petroleum gas (LPG) exports to China via rail by almost a third in the first half of the year to 133,000 metric tons, Reuters calculations, based on data from industry sources, showed on Wednesday.

The fuel supplies are still curbed by infrastructure constraints and congestion on Russian railways. According to the data, supplies in June declined by 16.5% from May to 12,300 tons, falling for the second month in a row.

Traders said that railcar congestion was especially pronounced at the Zabaikalsk-Manchuria border crossing due to maintenance work at the Manzhouli Far East Gas terminal in May and June.

Russian railway station Zabaikalskaya was also undergoing reconstruction, they said.

The sources said that supplies from Irkutsk Oil Company's (INK) Ust-Kut gas processing plant contributed most to the first-half increase, boosting supplies by 37,200 tons year-on-year.

INK accounted for almost 70% of Russia's LPG exports to China in January - June. Other large suppliers are Novokuibyshevsk Petrochemical Company, BerezkaGas and Taneko.

LPG, or propane and butane, is mainly used as fuel for cars, heating and to produce other petrochemicals.

In 2023, Russia raised rail exports of liquefied petroleum gas (LPG) to China by 35% to 202,000 tons.

Russia also supplies LPG by trucks. (Reporting by Reuters; Editing by Sharon Singleton)