Kolkata: Over 20 people were injured in clashes between rival political groups as over one crore voters cast their ballot in the first six hours in West Bengal's 17 parliamentary constituencies where polling is under way on Monday.

The opposition political parties accused the ruling Trinamool of unleashing violence to intimidate voters in various areas. They also claimed that a number of their polling agents were driven out of the booths. The Trinamool denied the allegations.