Russia's energy giant Gazprom said Ukraine had failed to pay at least part of its gas debts by this morning's deadline and must now pay up front for its energy supplies.
Gazprom said Ukraine has not yet paid for June supplies. The two countries failed to reach a deal on gas prices.
More top news
Up to three million children risk going hungry over the school holiday, with increasing numbers of families relying on food banks, MPs warn.
Tuesday will be a cold and windy day across the British Isles with a mix of sunshine and showers.
Some 71% of all cancer patients diagnosed in A&E had seen their GP at least once displaying symptoms which transpired to be the disease.