Image copyright AFP Image caption Two French women react as police use batons to disperse demonstrators
Officers were filmed using batons on protesters in Brussels as their fight against an Italian proposal to lower the voting age to 16 continued.
Protesters also clashed with police in the northern port city of Bremen, Frankfurt and Paris.
The government in Italy is to make the proposal at a parliamentary meeting later.
Protests have taken place in several European countries as a result of the move.
Concerns that the move could become another stain on the image of the European Union have also fueled opposition.
In Brussels on Friday, several hundred people blocked traffic on the A1 motorway outside the European Union institution, shouting “Europe is our future” and “Right to vote!”
Hundreds of protesters rallied in Bremen to object to the Italian proposal and said they wanted a referendum on whether or not lowering the voting age should be banned in Germany.
Lithuanian riot police used tear gas and stun grenades to control violent protesters
The proposal was made by Italian Interior Minister Matteo Salvini as part of his anti-immigrant strategy to make the country safer.
Following media reports that his populist party, the League, had supported the move, he was forced to deny any such support – but said if it were legal he would lead a campaign to lower the age of voting.
In England, Vote Leave had no involvement with the Italian proposal, Vote Leave said, while insisting it had no plans to introduce a similar change.
France was also rocked by violent protests as protesters with the group Train Eight tried to shut down the country’s high-speed trains.
The group was opposing the Interior Minister’s plans to close down some stations near Paris. They were arrested, but most of the disruptions were short-lived and trains continued to operate.