Russia halts gas supply to Ukraine
Ukraine says Russia has cut off all gas supplies to Kiev, in a major escalation of a dispute between the two nations.
"Gas supplies to Ukraine have been reduced to zero," Ukrainian Energy Minister Yuri Prodan said.
Russia's state-owned gas company Gazprom said Ukraine had to pay in advance for its gas supplies, after Kiev failed to settle its huge debt.
Gazprom had sought from Kiev $1.95bn (£1.15bn) - out of $4.5bn it says it is owed - by 06:00 GMT.
BBC World's Aaron Heslehurst reports.