Ukraine says Russia has cut off gas supplies, in what is a major escalation of a dispute between the countries. Gazprom, the Russian state energy firm, has pledged to continue supplies to Europe, but says it is Ukraine's responsibility to ensure gas flows through the country. BBC examine what's behind the row, and its potential impact on Europe and its gas supplies.
Ukraine's Energy Challenge
BBC: Red bills and red rags in Ukraine-Russia gas row
Ukraine on June 16 accused Russia of cutting supplies of gas after talks between the two countries passed a deadline set by Moscow without a deal on outstanding payments.
