Russia's state-controlled energy company Gazprom said it filed a lawsuit against Ukraine in Stockholm arbitration court.
Gazprom said it wanted to recover the £2.7 billion ($4.5 billion) Ukraine owes it for its gas supplies.
Talks between Ukraine and Russia over their ongoing gas pricing dispute have ended with no deal reached, a spokesman for Russian producer Gazprom said.
More top news
Georgina Callander's family said the government must "opens its eyes" in the wake of the attack.
Thunderstorms affect many throughout the rest of the Bank Holiday weekend.
Police have released CCTV images of the Manchester suicide bomber on the night of the arena attack.