Image copyright AFP Image caption Argentine President Cristina Fernandez de Kirchner has defended the country's claim to the islands

Argentina's decision to display signs expressing the country's claim over the Falklands is "regrettable", a diplomatic source has said.

A law passed by the Argentine Congress says public transport must have signs saying "Las Malvinas son Argentinas" (the Falkland Islands are Argentine).

The Argentine MP behind the initiative said it would reflect "our undeniable sovereignty" over the islands.

But the source said the move was a "hostile course of action".

The move was introduced as part of a wider raft of public transport reforms which were passed unanimously on Thursday.

Senator Teresina Luna, the member of Congress who proposed the new regulation, wrote to the president of the parliament to say: "It is directed not only at the foreigner who comes here as a tourist or visits our country, but also at the citizens in general, and will serve to reinforce our history, our culture and our identity."

Argentina lays claim to the islands, which it calls Las Malvinas, but Britain maintains that it has sovereignty and has accused Argentina of ignoring the wishes of the island's residents who wish to remain British.

Last year, Falkland islanders took part in a referendum, voting by 1,513 to three to remain a British overseas territory.

UK Prime Minister David Cameron said at the time that the result "could not have sent a clearer message" but Argentine President Cristina Fernandez de Kirchner has maintained that the islanders' wishes are not relevant.

The source added: "No sign can change the rights of the Falkland islanders to their own identity and we are determined to uphold that right."