The 27-member European Union on Monday formally banned all dealings in Russian central bank reserves and assets, except for transactions absolutely vital to individual member states or the bloc as a whole. The ban is part of sanctions against Moscow in response to its military operation in Ukraine which began last week.

“Competent authorities may authorize a transaction where strictly necessary to safeguard the financial stability of the Union as a whole or of the Member State concerned,” writes the EU in the regulation published in its Official Journal.

In the decision, Brussels also closed much of European airspace to Russian airlines.

European Commission President Ursula von der Leyen announced on Sunday that the bloc would ban several Russian banks from the global money transfer system SWIFT and ban RT and Sputnik News from broadcasting in the EU.

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Many countries, including the United States and Britain, imposed sweeping restrictions on Russia soon after its troops began attacking targets in Ukrainian territory early Thursday morning. Moscow said it was defending the people's republics of Donetsk and Luhansk, which broke away from Ukraine after the 2014 coup in Kiev. Ukraine said the attack was unprovoked and asked for help from the international community.

Ukraine has agreed to talks with Russia as fighting is reported near Kiev and elsewhere in the country. Negotiations are due to begin Monday morning near the Ukrainian-Belarusian border.