In a drive to win more seats at next week's European elections, nationalist parties from across Europe have come together in a show of unity that aims to forge a populist alliance that would be one of the largest groupings in the European Parliament.

Led by Italian Deputy Prime Minister Matteo Salvini, supporters gathered in a central Milan square to present a common front that aims to reshape the continent and pull back power from Brussels.

Far-right and anti-immigrant leaders from 11 European Union countries, including France's Marine Le Pen and Netherland's Geert Wilders, came together to set their sights on gaining more power within the bloc.

Salvini, leader of Italy's anti-immigrant Northern League party, promised the elections would help restructure the continent by boosting the far right.

Salvini is confident his newly forged alliance will win a record number of seats at the May 23-26 election, giving it a powerful voice in how the 28-nation EU is run over the coming five years.

"I think lots of things will change in Europe," Salvini said, adding that his group would remould Europe "not for our sake, but for our children".

"There are no extremists, racists or fascists in this square," he claimed.

"The extremists are those who have governed Europe for 20 years."

Protesters opposed to the rally converged on a park nearby, and local residents hung banners that announced "Milan is anti-fascist" from their windows.

Salvini and Le Pen hope their Europe of Nations and Freedom group, currently only small in the European Parliament, will become the third-largest.

"This is an historic moment," said France's National Rally (RN) leader Le Pen, who told the crowd that Europe had to be protected from uncontrolled immigration that had brought millions of refugees and asylum seekers to the continent since 2014.

"We say no to this immigration which has submerged our nations, putting our people at risk," she said, playing up an issue that has helped fuel support for nationalist groups.

The parties in the group share the same intentions; to return power to EU member states, curb immigration, and prevent the spread of Islam in Europe.

But there are many concerns that divide the alliance as many of the parties have different social and economic policies.

Reuters reported recent polls suggest Salvini's alliance will end up with the fourth-largest bloc of seats in the next EU Parliament, but Le Pen said a number of other parties might eventually join it, including Hungarian Prime Minister Viktor Orban's Fidesz Party, which is currently anchored to Europe's mainstream right.

The newly formed alliance suffered a setback when Austria's Freedom Party had to skip the rally, as its leader Heinz-Christian Strache quit as government vice-chancellor after he was videoed offering state contracts in exchange for political support.

Some top EU jobs will become vacant after the elections, including president of the European Central Bank, and Salvini hopes a strong showing by nationalists will give them more influence when the posts are filled.

Massimiliano Panarari, a politics professor at Rome's Luiss University, told the Guardian that the main goal of the alliance is "tactical".

"It doesn't matter if they have different positions, it's about political marketing-presenting themselves as an alternative to the current Europe-and having power in the European institutions," he said.