Riot police were called to the European Parliament this evening, after demonstrators attempted to enter the building to protest against the presence of the French National Front leader Marine Le Pen.
Police with shields and helmets were posted at the parliament's doors and people were prevented from leaving or getting into the building.
Leftist demonstrators shouted: “Fascists in jail” as they went to different doors of the parliament.
Ms Le Pen spoke to journalists in parliament, along with other far-right leaders from the Netherlands, Austria, Belgium and Italy.
They announced their plans to form a political grouping in the new parliament and block any further moves towards a federal Europe.
Ms Le Pen said parties from five different countries were signed-up to the new grouping and she was confident of securing the necessary two more before the deadline in three weeks.
With her today were leaders of Belgium's far-right Vlaams Belang (VB), the Dutch Party for Freedom (PVV), the Freedom Party of Austria (FPO) and Italy's Lega Nord.
Also trying to form a eurosceptic grouping is rival anti-EU leader Nigel Farage, the head of the UK Independence Party who like Ms Le Pen topped national polls, and also picked up 24 seats in the EU assembly.
"We aren't worried in the least about the future existence of our group," said Ms Le Pen.
"Farage heads a group and wants to keep it," she added. "Sorry Nigel but we're going to set up our group."
Her Dutch ally Geert Wilders of the anti-Islam anti-immigrant PVV said he was "very confident that maybe not tomorrow but in the next few weeks" the five far-right parties would find the extra two allies needed.
If officially recognised as a group, the Front and its allies would win the right to express an opinion on any issue raised in plenary session and take the presidency of any of the parliament's 20 committees and two sub-committees.
Its president would help draw up the agenda of the plenary sessions and get the right to reply directly in plenary session to the heads of the European Commission and the European Council.
It would also be given a secretariat, offices and aides paid by Parliament. Last year the Parliament's seven outgoing political groups shared a budget of €57 million.
On top of this, the group would benefit from extra subsidies paid out to pan-European parties such as the €400,000 a year currently handed to the Malta-based European Alliance for Freedom (EAF).
Depending on how many MEPs it had, it could win anywhere between €1m and €3m a year.
A group however must have at least 25 MEPs.