Voters in 19 EU countries are casting ballots in the final round of the election for the European Parliament.
A number of nations - including Britain, Ireland, the Netherlands and the Czech Republic - have already voted.
The BBC reports a total of 736 seats in the European Parliament are at stake.
The voting schedule is:
Thursday: UK and Netherlands
Friday: Ireland, Czech Republic
Saturday: Latvia, Cyprus, Malta, Slovakia, Italy and Czech Republic
Sunday: Austria, Belgium, Bulgaria, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Italy, Lithuania, Luxembourg, Poland, Portugal, Romania, Slovenia, Spain and Sweden