Russia's Finance Minister Anton Siluanov announced the creation of an anti-crisis fund to help the companies that have been targeted by the US, according to the RIA Novosti news agency.

Part of the funding for the project would come from the country's pension fund, while the rest would be provided by cash leftover from the 2014 budget.

A total of 309bn roubles ($8.1bn, £5bn, €6,3bn) would be diverted from the pension fund back into the budget, while the new fund would receive at least 100bn roubles, Siluanov was cited as saying by Russian news agencies.

"We are planning to create a reserve of significant size," he said, as quoted by RIA.

"This 100 billion roubles will be added to the reserve next year, which will allow us to help our companies."

Meanwhile, on 15 September, Russian Prime Minister Dmitry Medvedev said the country's strength had been tested by Western sanctions, urging his countrymen not to overreact to the sanctions campaign.

"When a series of our partners, if they can be called that, test Russia's strength through sanctions and all kinds of threats, it is important not to succumb to the temptation of so-called easy solutions and to preserve and continue the development of democratic processes in our society, our state," said Medvedev, in a televised address.

The Kremlin has increasingly adopted a siege mentality in its public response to the incremental economic sanctions passed by the West.

The European Union and the United States imposed a new round of penalties against Russia on 12 September, restricting some of Russia's biggest companies' access to Western capital markets.

The EU measures targeted Russian oil companies Rosneft and Transneft, while the petroleum arm of Russia's state-run gas giant Gazprom was also blacklisted.

The US imposed penalties on Russia's biggest bank, Sberbank, and conglomerate Rostec, while US companies have been prevented from doing business with five Russian energy companies involved in deepwater, Arctic offshore and shale operations.

The latest measures were imposed after a ceasefire was agreed between separatist rebels and Ukraine's government forces in the east of the country.

Russian President Vladimir Putin said the measures were "strange," while a foreign ministry spokesman said the Kremlin was preparing retaliatory measures.

The Western allies said the sanctions could be reversed if Russia was to withdraw all its forces from Ukrainian territory. Russia has denied accusations that its troops are present in Ukraine.

More than 3,000 people have been killed since fighting erupted in eastern Ukraine in mid-April.