Russia increased the pressure on Ukraine yesterday as President Dmitry Medvedev ordered Gazprom to enforce payment of $2.4bn (£1.6bn) in gas debts.

"We need to clarify our position on Ukraine's debt and recover it either on a voluntary or compulsory basis," Mr Medvedev told Alexei Miller, the Gazprom chief executive, in comments broadcast on Russian television. Mr Miller later said Gazprom would charge Ukraine more than $400 per thousand cubic metres for gas next year, more than double the $179.5 Kiev currently pays.