Argentina will present a formal complaint at the United Nations over Britain's "militarisation" of the situation in the Falkland Islands.

"We will present a complaint to the UN Security Council and the UN General Assembly, as this militarisation poses a grave danger to international security," said President Cristina Kirchner.

The two sides have ramped up the rhetoric in the run-up to the 30th anniversary of the war.

The conflict broke out on 2 April 1982, when the ruling junta in Buenos Aires invaded the disputed islands in a bid to end British rule.

Argentine officials have expressed anger in recent weeks after the deployment of a British warship and the dispatch of Prince William for a tour of duty as a helicopter pilot.

Britain "is once again in the process of militarising the south Atlantic," Ms Kirchner said.

"We cannot interpret in any other way the deployment of an ultra-modern destroyer accompanying the heir to the throne, who we would prefer to see in civilian attire."

Hundreds of protesters rallied near the government palace where Ms Kirchner was speaking, waving Argentine flags and shouting: "Malvinas! They belong to us!" referring to the islands as they are known in Argentina.

Britain has held the Falkland Islands since 1833.