Bosnian Serbs, whose leaders have repeatedly threatened to secede, cannot follow the example of Crimea which joined Russia after a referendum, Britain's foreign secretary told a local paper Friday.

"Let me be clear, there can be no more re-drawing of borders in the Balkans," William Hague said in an interview with the Dnevni Avaz daily.

"Only a single, sovereign Bosnia-Hercegovina within its current borders can join the European Union.

"This is a belief which I share with all of my colleagues in the 28 EU member states," the British minister said, according to quotes in English obtained from the paper by AFP.

Since the end of its inter-ethnic war in the 1990s Bosnia consists of two entities -- the ethnic Serbs' Republika Srpska and the Muslim-Croat Federation.

The two-highly autonomous halves share weak central institutions while each has its own government and parliament.

Ukraine's Crimea region voted to become part of Russia in a referendum earlier this month and was then rapidly incorporated into Russian territory.

Hague, who arrived in a visit to Bosnia late Thursday, stressed there was "simply no valid comparison to be drawn between the entity of Republika Srpska and the Crimea".

"The actions taken by Russia in Ukraine are an appalling example of illegal annexation, which European Union member states have been united in condemning."

Bosnian Serb President Milorad Dodik has long sought the secession of his entity from Bosnia.

Bosnian Serbs strongly oppose any strengthening of the country's joint institutions, a move sought by both Muslims and the international community.

The Balkan country's 1992-1995 war between its ethnic Croats, Muslims and Serbs left some 100,000 dead.