Russia on Saturday slammed the EU's extension of sanctions over its annexation of Crimea as "blackmail" and vowed it would not be pressured into returning the peninsula to Ukraine.

"Crimea and Sevastopol are an integral part of the Russian Federation. It's time to recognise this as a fact that cannot be changed with methods of economic and political blackmail," a statement by the Russian foreign ministry said.

Sanctions have "no prospects," the statement said, further criticising the EU's decision Friday as "discrimination" and comparing them with "historical examples of collective punishment of nations."

Russia annexed Crimea in March 2014 following the ouster of Ukraine's pro-Moscow president Viktor Yanukovych.

The Kremlin pointed to the results of a controversial referendum, which showed overwhelming support among Crimeans for a return to Moscow rule, as justification for the move.

In response, the EU imposed asset freezes and visa bans on pro-Moscow rebel leaders and Russian figures it said had conspired to strip Ukraine of Crimea.

As the Ukraine crisis deepened, the bloc widened the sanctions list over Crimea -- while also imposing economic sanctions on Russia over its alleged involvement in an insurgency in Ukraine's east -- to include a ban on imports from and investment in the peninsula.

Friday's decision covered the sanctions agreed in June 2014, which also included bans on cruise ships using Crimean ports and restrictions on exports of telecommunications and transport equipment.

The measures will last until June 2016, the 28-nation bloc decided, condemning the "illegal annexation" of the Black Sea peninsula.