The cost of insuring Ukraine's debt against restructuring or default rose to its highest since the 2004 Orange Revolution yesterday, as investors fretted that the Kremlin's spat with the west could spill over into a vast country of 46m people that straddles the divide between a resurgent Russia and the European Union.

Worries about the debt intensified after a dispute over Russian warships' use of the Ukrainian Black Sea port of Sevastopol highlighted tensions between Russia and Ukraine, which became independent from Russia following the collapse of the Soviet Union.