With fighting unrelenting in Ukraine’s east, Western sanctions have fired a further warning shot at Russia.

The US will now extend credit freezes to a number of key Russian companies, particularly in the energy sector.

Russian Prime Minister Dmitri Medvedev has already branded the tougher stance evil, whilst President Vladimir Putin noted the damaging effect to relations, saying that the sanctions might impact the US itself.

“(Sanctions) have a boomerang effect and without a doubt they will push US-Russian relations to a dead end and cause very serious damage,” he said. “I am also sure that this damages the national long-term strategic interests of the US government and US people.”

But the targeted measures are already having a domestic impact. Shares in Russia’s largest oil company Rosneft fell over five percent early on in trading, whilst shares of energy firm Novatek took a similar dive.

Both are headed by figures thought to be close to Putin.

Igor Sechin, Rosneft’s CEO, criticised the latest raft of sanctions.

“Since Rosneft is a budget-generating enterprise for Russia, those sanctions are not aimed at Rosneft as a company, they are aimed at Russia’s pursuit of its own sovereign politics and an attempt to aggravate the economic welfare of our citizens,” he said.

Eight weapons firms and two major financial institutions have also made the blacklist, and a raft of EU sanctions are set to curtail investment in Russia.

Western leaders continue to blame Moscow for not doing enough to end the violence in eastern Ukraine.