Russian energy company Gazprom said it has "stopped supplying un-paid-for gas to Ukraine" this morning, according to reports in Russian media.
Gazprom said Ukraine has failed to pay for its gas supplies.
A Gazprom spokesperson told ITV News the company will now require all payments to be made in advance.
More top news
When Alison Powell's four-year-old Labrador Missy would not stop sniffing and pawing her, she knew it was more than simple canine affection.
Police have confirmed that six arrests were made as part of their operation for the Arsenal v Galatasaray Champions League match
A Banksy mural, possibly worth thousands of pounds, has been erased by a council in Essex after a complaint that it was "racist".