By Pavel Polityuk and Olena Harmash
KYIV (Reuters) - Ukraine hopes to store around 4 billion cubic metres (bcm) of gas for foreign companies and traders this winter, up 60% from last year, despite Russian airstrikes on the country's energy infrastructure, the head of Ukraine's state energy firm said.
Storing gas helps Ukraine to collect revenues while providing Europe with additional supply flexibility after the continent cut Russian gas imports because of Moscow's invasion of Ukraine.
Oleksiy Chernyshov, chief executive of Naftogaz, told Reuters Russia had attacked the firm's infrastructure five times since March, in the first such attacks since the war began in February 2022.
He said the underground storage was not damaged but Naftogaz was working on strengthening defences as gas pumping facilities above ground are more vulnerable.
Underground facilities, mostly in western Ukraine, have a capacity of 31 bcm. That is enough to cover Ukraine's annual needs and allow storage of surplus volumes from Europe to be released during peak demand in the northern hemisphere winter.
Chernyshov said foreign traders had resumed pumping gas into the storage in recent days. He said volumes were small so far, but he expected them to rise later this year when the heating season approaches.
He did not provide volumes of gas stored so far or the name of those that have stored gas.
Traditionally, Ukraine's storage was used by neighbours such as Poland, but Naftogaz has said it has spoken to firms as far away as France to boost the number of customers.
"We are in a period of European shippers' meetings where we agree on the volumes of (gas) injection. They (the Russians) aim to discredit us as an energy hub with storage capacities," Chernyshov said.
Russian officials have said Moscow was attacking Ukraine's energy facilities in retaliation for Ukrainian drone attacks on Russian refineries.
Chernyshov said the company had about 100 contracts with foreign traders to store gas. Russia continues to supply gas to Europe via Ukraine under a transit deal that is set to expire in December. Ukraine has said it does not plan to renew it.