Demonstrators have attacked the British embassy compound in Buenos Aires on the 30th anniversary of the start of the 1982 Falklands War.
Members of the extremist Quebracho movement charged the compound in the Argentine capital after smashing through a protective barrier.
Riot officers forced them back before some demonstrators launched missiles and flares at police, who returned fire with rubber bullets, water cannon and tear gas.
In the minutes prior to the attack, extremists had set fire to a Union Jack flag and an effigy of Prince William, the Duke of Cambridge.
Speaking to Sky News Online, Quebracho leader Fernando Esteche, said: "The burning of the flag and effigy symbolised our disgust at this British invasion of our national territory.
"This includes Britain's monarchy, which is directly responsible."
In a statement the Foreign Office said: "We condemn the violent actions of a minority during today's demonstration.
"All states are obliged under the Vienna Convention to provide appropriate protection for foreign diplomatic missions.
"We expect the Argentine government to continue to fulfil its obligations under the convention and continue fully to enforce the law against any demonstrators committing criminal acts.
"We recognise the dedication and professionalism of the police in their efforts to keep order."
Many Argentines believe British presence in the South Atlantic is an illegal act of colonialism.
"We smashed the barrier down to show you (the British) that you can't erect barriers in our country, that we have a right to protest," said the 43-year-old.
Elsewhere in the capital, on the eve of the anniversary, Argentina's Falkland War veterans observed a midnight vigil at the national memorial to the 649 killed in the 1982 conflict.
Dressed in full combat fatigues and sporting war medals, veteran Ricardo Rojas, said: "April 2, 1982, was a glorious day, on which we finally said enough to British colonialism.
"If we have to return to the islands, we will, just like in 1982. If we go back to war, I will be the first to sign up. If the government thinks military action is needed it has my full support.
"We will never give up our land. These islands belong to Argentina and always will," said the former combatant, who was 20 years old when Argentina's then-ruling military junta conscripted him to fight in the war.
As part of Argentina's Marine Infantry Battalion he fought British troops at Mount Tumbledown.
The veterans ended their midnight vigil with cries of Viva la Patria! and a gun salute.
Meanwhile, Argentina's president, Cristina Fernandez de Kirchner, led an official act of commemoration in the southern city, Ushuaia .
The choice of Ushuaia was symbolic. It is capital of the Tierra del Fuego province, which Argentines believe the Falklands form a part of, and faces the islands from Argentina's coast.
It was the centre of Argentine military operations in the 1982 war.