Europe's main stock markets closed with gains on Wednesday after a day of seesaw trading as the euro rose sharply against the dollar.

London's benchmark FTSE 100 index eeked out a 0.09 percent gain to 6,933.74 points on the eve of Britain's most unpredictable election in living memory.

The CAC 40 in Paris rose 0.15 percent to 4,981.59 and the DAX in Frankfurt climbed 0.20 percent to 11,350.15 points.