KIEV, June 6 - Ukraine’s imports of natural gas from Russia increased by 351% year-on-year, or by 2.9 billion cu m, to 3.7 billion cu m in May, up from 820 million cu m imported in May 2013, the state-owned natural gas shipping company UkrTransGaz reported Friday.

Ukraine’s imports of Russian gas in May also rose 39.1% month-on-month from 2.66 Bcm imported in April, the company said.

Ukraine stepped up imports of natural gas over the past two months to replenish gas stocks in its underground storage facilities amid fears that Russian gas supplies may be disrupted in June.