McDonald's announced today it has closed its restaurants in Crimea, prompting fears of a backlash as a prominent Moscow politician called for all the U.S. fast-food chain's outlets in Russia to be shut.

Crimea's annexation by Russia, which Ukraine and the West do not acknowledge, has worried companies with assets in the Black Sea peninsula as it is unclear how the change may impact their business.

While McDonald's did not mention the political situation in its statement, its decision to leave the region is likely to be seen as emblematic of the rift in Western-Russian relations, now at their lowest ebb since the end of the Cold War.

"Due to operational reasons beyond our control, McDonald's has taken the decision to temporarily close our three restaurants in Simferopol, Sevastopol and Yalta," a spokeswoman said.

'It would be good if they closed here too ... if they disappeared for good. Pepsi-Cola would be next.'-Vladimir Zhirinovsky, deputy speaker of Russian parliament

McDonald's said it hoped to resume work as soon as possible, but it would help relocate staff to work in mainland Ukraine, signalling it did not expect its Crimean businesses to reopen in the near future.

The Crimean outlets are not franchises, but owned and operated by McDonald's itself.

The closures follow Geneva-based Universal Postal Deutsche Post's announcement that it was no longer accepting letters bound for Crimea as delivery to the region was no longer guaranteed.

Economic relations between Russia and Ukraine have worsened since Russia annexed Crimea last month.

Targeted sanctions imposed on a number of prominent Russians by the U.S. and the EU have alarmed some foreign investors.

Russia raised the price it charges Ukraine for gas on Thursday for the second time this week, almost doubling it in three days and piling pressure on its neighbour as it teeters on the brink of bankruptcy.

Moscow has frequently used energy as a political weapon in dealing with its neighbours, and European customers are now concerned Russia might again cut off deliveries.

'Pepsi-Cola would be next'

The company's decision was welcomed by the deputy speaker of the Russian parliament, Vladimir Zhirinovsky, known for his anti-Western rhetoric, who demanded that McDonald's pull its business out of Russia entirely.

"It would be good if they closed here too ... if they disappeared for good. Pepsi-Cola would be next," Russian media quoted Zhirinovsky as saying.

Zhirinovsky, whose nationalist Liberal Democratic party largely backs President Vladimir Putin in parliament, said the party would organize pickets at McDonald's restaurants across the country.

McDonald's, which currently operates more than 400 restaurants in Russia, was the first international fast-food chain to tap the Russian market when it opened in Moscow's Pushkin Square before the collapse of the Soviet Union.

That branch had the highest sales and served the most customers of any McDonald's outlet in 2012.

A Russian backlash against McDonald's products would have a significant impact on company profits.

McDonald's sees Russia as one of its top seven major markets outside the U.S. and Canada, according to its 2013 annual report.