Fears are growing of Russian reprisals against European businesses as EU authorities desperately seek a deal to save the Cypriot economy by imposing a 25% levy on bank deposits of more than €100,000.

As the island scrambled to put together a rescue programme, its finance minister, Michalis Sarris, said "significant progress" had been made on the latest levy plan in talks with officials from the European Union, the European Central Bank and the International Monetary Fund.

The government in Nicosia faces a deadline of Monday to reach an agreement or the European Central Bank says it will cut off emergency cash to the island, spelling the likely financial collapse of its banking system and a potential exit from the European single currency.

However, with Russian investors having an estimated €30bn (£26bn) deposited in banks on the island, the growing optimism about a deal was accompanied by fears of retaliation from Moscow. Alexander Nekrassov, a former Kremlin adviser, said: "If it is the case that there will be a 25% levy on deposits greater than €100,000 then some Russians will suffer very badly.

"Then, of course, Moscow will be looking for ways to punish the EU. There are a number of large German companies operating in Russia. You could possibly look at freezing assets or taxing assets. The Kremlin is adopting a wait and see policy."

Nekrassov rejected suggestions that Russia might hit back by cutting off gas supplies, a tactic the country used in 2009 after the collapse of talks with Ukraine to end a row over unpaid bills and energy pricing.

"Gas is no longer a weapon," Nekrassov said. "When Russia did that before, it realised that the foreign energy lobby reacted and efforts to find alternative sources were increased. If Russia kept threatening, it knows that nobody would be buying its gas in 20 years' time."

Mike Ingram, an analyst at City broker BGC Partners, said: "In Russia, historically, if they want an asset they just grab it. If they want cash out of a [EU] business [in Russia] they just create a tax bill or raid offices and make your life unpleasant. They could also make life difficult diplomatically on issues such as Syria. They might also rattle a few sabres over deployment of the missile defence system."

In a week of high-stakes brinkmanship, the EU, ECB and IMF – the so-called "troika" behind the rescue of five southern European countries – had refused to budge on its insistence that Cyprus raise €5.8bn of its own revenues to qualify for the bailout aid.

The latest levy plan reflected Nicosia's fast-dwindling options.

Last week Cypriot MPs overwhelmingly rejected a similar levy proposal – even after it was adjusted to remove any charge on savings below €20,000 – triggering a week of tumult as Nicosia tried and failed to win financial support from Russia instead.

The tax on savings is unprecedented in Europe's handling of a debt crisis that has spread from Greece to Ireland, Portugal, Spain and Italy. The crisis has reignited uncertainty about the future of the eurozone just as many EU leaders began to believe the worst was over for the single currency.

On Saturday, uncertainty shrouding the island turned from unease on the streets, where people have rushed en masse to withdraw money from cash machines, to scenes of panic-buying.

The inept handling of the crisis by politicians has exacerbated a dark mood with many Cypriots fearing that they stand to lose life savings following the government's decision to also raise funds by restructuring Laiki, the island's second biggest bank.

Marios Panayides, 65, a protester outside the Cypriot parliament said: "Our so-called friends and partners sold us out. They have completely abandoned us on the edge of an abyss."

Retailers, facing cash-on-delivery demands from suppliers, warned stocks were running low. "At the moment, supplies will last another two or three days," said Adamos Hadijadamou, head of Cyprus's Association of Supermarkets. "We'll have a problem if this is not resolved by next week."

Cypriots fear the damage the levy would do to the country's offshore banking industry. Much of the Cypriot banks' capital was wiped out by the collapse of investments in Greece, the epicentre of the euro zone debt crisis.