"The demand of Ukraine for Russian gas has increased twofold from May 1," Miller told RIA Novosti.
According to Ukraine's gas transmission and storage company Ukrtransgaz, Gazprom has delivered 261 million cubic meters of gas to Ukraine in the period of April 1-27, with Ukraine using approximately 9.6 million cubic meters of gas daily.
Last summer, Gazprom transferred Ukraine to a prepayment system for gas deliveries due to latter's immense debt, surpassing $5 billion at the time.
Moscow and Kiev signed a "winter package" deal in October 2014, which guaranteed deliveries of Russian gas to Ukraine with a discount of $100 per 1,000 cubic meters until the end of March.
On March 31, Russia extended the discount for the second quarter of 2015 due to Ukraine's economic problems.
