Argentina has lodged a protest with Brazil for hosting British military aircraft flying to and from the Falkland Islands.

Argentina’s government said the Royal Air Force made 18 flights between the Falklands and airports in Brazil over the last two years. Buenos Aires called them a breach of agreements among South American countries.

The Argentinian foreign ministry said in a statement it was “concerned” about six flights last year and 12 in 2015. The ministry said it had requested an explanation from Brazil’s government, reminding it of that country’s commitment “to not allow British airplanes or warships based in the disputed archipelagos”.

“The Brazilian foreign ministry reaffirmed its support to our country on this issue and said that it was unaware of these flights,” the Argentinian statement said.

Brazil’s foreign ministry had no immediate comment on the issue.

Argentina lost a brief but bloody war with Britain after invading the South Atlantic archipelago in 1982.

The war over the islands known by Argentina as the Islas Malvinas claimed the lives of 649 Argentinian and 255 British servicemen.

During her eight years as Argentina’s president, Cristina Fernandez tried to pressure Britain into sovereignty talks by turning away British ships, encouraging companies to divest from Britain and raising other trade barriers. Tensions have eased since pro-business Mauricio Macri succeeded her as president in 2016 promising a less confrontational stance.

In the biggest breakthrough in decades, Britain and Argentina announced in 2016 that they would work to remove restrictions in the oil, fishing and shipping industries affecting the Falklands. They also agreed to increase the number of flights between the islands and Argentina.

The Falklands are internally self-governing but Britain is responsible for defence and foreign affairs. Argentina claims Britain has illegally occupied the islands since 1833. Britain disputes that and says Argentina is ignoring the wishes of its 3,000 residents who want to remain British.