"The declaration of independence of Kosovo came after the failure of all the efforts of the international community to find a negotiated solution between Belgrade and Pristina on the status of Kosovo," Bulgarian news agency BTA quoted the statement as saying.
Serbia, which says it will never recognize its predominantly Albanian province as an independent state, has repeatedly warned that its relations with countries that recognize Kosovo are bound to be damaged.
Russia has been a leading international opponent of Kosovo's drive for independence, and has linked recent unrest in Tibet to international recognition of Kosovo.
Before today's announcement, a total of 30 states, including the United States and 18 European Union members, had recognized the republic's February 17 declaration of independence.
Of the 27 EU states, Spain, Cyprus, Malta, Lithuania, Romania, Greece and Portugal have yet to recognize the republic.
In their statement, EU members Bulgaria and Hungary, and EU candidate country Croatia, also spoke for further development of ties between Serbia and the European Union and for a strengthening of good-neighborly relations with Serbia.
The statement called Kosovo a "sui generis case arising from the unique circumstances of the disintegration of former Yugoslavia as well as the continued period of international administration."
Serb Foreign Minister Vuk Jeremic, on a visit to Athens, issued a statement to reporters urging the three countries not to recognize Kosovo, saying they would be violating Serbia's sovereignty by such a decision.
Russia and Serbia insist that Kosovo is not a unique case, and that its precedent will boost separatist sentiment in breakaway provinces throughout the world.
Soon after Kosovo's declaration, two breakaway Georgian territories, Abkhazia and South Ossetia, along with Moldova's Transdnestr, asked Russia's parliament, the United Nations and other organizations to recognize their independence.
