Russia has been boosting its oil supplies to the Asia-Pacific region as it expanded its pipeline network eastwards with the 4,740 km-long (2,945 miles-long) East Siberia-Pacific Ocean (ESPO) pipeline to diversify its supply markets.

Russia has been China's largest oil supplier for the past three years, after taking the top spot from Saudi Arabia.

Last year, Russian supplies to China rose to 71.49 million tonnes, or 1.43 million barrels per day, up 19.7 percent from 59.7 million tonnes in 2017.

According to Transneft, oil supplies from Russia's eastern-most port of Kozmino, opened in 2009, declined last year to 30.4 million tonnes from 31.7 million tonnes in 2017.

China was by far the main destination for oil from Kozmino, accounting for 80.1 percent of all loadings last year, up from 72.8 percent in 2017.

Oil from Kozmino also went to Japan (8 percent), South Korea (5 percent), Singapore and Malaysia (2 percent each).