Nigel Farage, UK Independence Party (UKIP) leader, met with Beppe Grillo, who heads Italy's anti-establishment 5-Star Movement, on Wednesday (28 May) in Brussels to discuss a potential alliance between Eurosceptic parties in the European Parliament.
Both groups performed strongly in last weekend's European Parliament vote, with UKIP topping all rivals in Britain and 5-Star coming in second to the ruling Democratic Party.
Farage and Grillo agreed on the importance of direct democracy in Europe and that the parties in a potential new group should be able to campaign and vote as they choose within a framework of basic agreements, UKIP said in a statement.
"If this works out it would be magnificent to see a swelling in the ranks of the Peoples' Army. If we can come to an agreement, we could have fun causing a lot of trouble for Brussels," the statement quoted Farage as saying.
It quoted Grillo as saying, "we are Rebels with a Cause, and we shall whistle as we march."
Grillo was spotted by Matteo Salvini - leader of Italy's anti-euro, anti-immigrant Northern League party - on a plane to Brussels early on Wednesday. Salvini later Tweeted that he had had a "long and interesting chat" with Grillo on the plane.
Chased by Italian television news cameras at the airport, Grillo did not comment when asked about the meeting, but later posted on his blog: "The 5-Star Movement is here to stay and to make a difference in Europe."
Anti-establishment parties across the continent more than doubled their representation in the election, tapping into voters' anger with Brussels over austerity, mass unemployment and immigration.
UKIP wants an immediate referendum and for Britain to withdraw from the European Union, arguing that the country will be more democratic and prosperous outside it. Italy's 5-Star wants a referendum over Italy's membership of the euro, which Grillo says is ruining the economy.
The possibility of 5-Star joining an alliance with another political party - albeit in Brussels - is something of a novelty. In Italy, Grillo has refused to negotiate with political parties in parliament, where 5-Star is a member of the opposition, saying they lack credibility.
To form a political group in the 751-seat Strasbourg-based parliament, 25 members of parliament from seven states are needed. In the new legislature, UKIP will have 24 seats and 5-Star 17.
Far-right parties including the Front National and Dutch Freedom Party met on Wednesday (28 May) to discuss forming a new group in the European Parliament.
Separately, Northern League secretary Salvini, whose party has five seats in the new parliament, said he would meet with French National Front leader Marine Le Pen, who topped the vote in France.
Le Pen's far-right party won 24 seats.