Voters go to the polls in Denmark shortly in a referendum on a treaty which would allow some of the former communist countries of eastern Europe to join the European Union.

The treaty also calls for the introduction of common policies on immigration and asylum.

It was agreed by EU leaders last year, but must be ratified by all member nations.

A BBC correspondent in Copenhagen says a close vote is likely as many Danish voters are concerned about a loss of sovereignty.

Our correspondent says if they reject the treaty, it will damage many of the EU's plans for the future.