"This activity demonstrates that Ukraine's gas infrastructure is fully integrated into the European one," the ministry said in a statement.
Ukraine's biggest oil and gas firm Naftogaz has said that foreign customers could use more than 10 bcm of storage of the country's around 30 bcm capacity, mostly in the country's west, which is far from the front lines of the war with Russia.
Traders told Reuters earlier this year that European gas traders had begun storing natural gas in Ukraine to take advantage of lower prices and available capacity there, regardless of the risks from the war.
Since Russia's full-scale invasion of Ukraine in February last year, the European Union has sought high levels of gas storage to compensate for reduced Russian supply, especially during the peak-demand winter months.
