Energy major BP opened a new front in the West's campaign to isolate Russia's economy, with its decision to quit the oil-rich country the most aggressive move yet by a company in response to Moscow's invasion of Ukraine.

Western allies have ramped up efforts to punish Russia with new sanctions including shuttering their airspace to Russian aircraft, cutting some of its banks off the SWIFT financial network and limiting Moscow's ability to deploy its $630 billion foreign reserves — measures that are expected to pulverize the country's financial markets and economy.

BP, the biggest foreign investor in Russia, said it was abandoning its stake in state oil company Rosneft at a cost of up to $25 billion, shrinking its oil and gas reserves in half.