Argentina's President Javier Milei on Sunday threw his weight behind Europe's far right at a Madrid rally that also featured leading stars of the movement like Italy's Giorgia Meloni and France's Marine Le Pen.
The event organised by Spain's far-right party Vox came ahead of elections to the European Parliament from June 6-9.
Surveys suggest those will result in soaring gains for Europe's far right, giving it more influence in Brussels.
Milei urged Europe's ultra-nationalists to unite against "socialism" in his address to the rally at Madrid's Vistalegre congress centre, which was attended by some 11,000 people according to Vox.
"Let's not give in to socialism, let's face it with greater courage. It seems that we are few, but we have nothing to fear, because victory on the battlefield does not depend on the number of soldiers, but on the forces that come from heaven," he said.
"I will lead by example and show the world that a government with our ideas can succeed. It is up to me to show them how sinister and nefarious socialism is, because... Argentina has been infected by socialism for decades," he added.
A self-declared "anarcho-capitalist", Milei won elections last November vowing to reduce the Argentine deficit to zero.
To that end, the chainsaw-wielding, anti-establishment Argentine has instituted an austerity programme that has seen the government slash subsidies for transport, fuel and energy, even as wage-earners lost a fifth of their purchasing power.
The Argentine leader is the "example" that "it is possible to propose an alternative," one of the founders of Vox, Javier Ortega-Smith, told AFP.
"He is a good example for Spain," he added.
Milei, a burgeoning superstar on the global right who began his visit to Spain on Friday, will not be meeting Socialist Prime Minister Pedro Sanchez or King Felipe VI during his stay as usually is the case when a foreign leader visits.
Le Pen, France's far-right standard-bearer and former presidential candidate, told the crowd that "the real Europe, the Europe of freedom" needs nationalist forces to be "united".
"We are, all of us together, in the home straight to make June 9 a day of deliverance and hope," she added.
Like other speakers, Le Pen stressed the need for tighter restriction on immigration, a central theme of European far-right parties.
"Entire areas of my country, France, are being submerged by immigration and are no longer under the authority of the state," she said.
In video messages, Hungarian Prime Minister Viktor Orban urged "patriots" to "occupy Brussels", while Meloni, Italy's premier, called for a "mobilisation" to bring about "change in Europe".
In a message posted on social network X, Sanchez said the "international far-right" was meeting in Madrid "because Spain represents what they hate: feminism, social justice, labour dignity".
Hundreds of people, many holding up signs that read "no fascism!" protested in Madrid's central Plaza de Colon against the gathering.
Amid flags of Argentina, Mexico and Palestine, 27-year-old Argentinian Marisel Cherasco criticised Milei's policies because they "benefit a few at the expense of the well-being of the majority".
