Russia sharply hiked the price for natural gas to Ukraine today, raising the heat on its cash-strapped government, while Ukrainian police moved to disarm members of a radical nationalist group after a shooting spree in the capital, Kiev.

Russian forces have been accused of “an armed invasion” after units blocked a Ukrainian military airport in the Black Sea port of Sevastopol in Crimea.

Ukraine issued an arrest warrant yesterday for its ousted pro-Russian president over “mass murder” and appealed for $35bn (€25bn) in Western aid as Moscow denounced Kiev’s new reformist interim government as “Kalashnikov-toting people in black masks.”