Argentina protested against a UK vessel, HMS Medway, for its allegedly illegal approach to the Falkland Islands through Argentina’s territorial water, in a Thursday post on X (formerly Twitter) by its Foreign Minister Pablo Quirno. The post came after Argentina’s national team displayed a controversial slogan relating to the territory at the end of its FIFA semi-finals against England on Wednesday.

Argentina’s official statement, dated July 13, described the stationing of HMS Medway in the Falkland Islands as an “unconsulted and illegal military incursion” into its territorial sea, violating the 1991 joint declaration between the two nayions. The statement also accused the UK of violating its international duty to refrain form altering the territory’s situation unilaterally, in accordance with the UN General Assembly Resolution 31/49.

The UK government rejected the accusations. The spokesperson for Prime Minister Keir Starmer said in a press briefing that they informed Argentina of the logistics mission between Chile and the Falkland Islands to support the country’s research in Antarctica, according to The Guardian.

Commentators also argued that HMS Medway was merely exercising her right to passage under the UN Convention on the Law of the Sea. The right allows any ships to navigate through a state’s territorial sea in a way that does not threaten the sovereignty of the coastal state or compromise its rights in the territorial sea.

The UN considers the Falkland Islands one of the world’s remaining non-self-governing territories. They enjoy the right to self-determination under the UN Charter and international covenants. The right entails that people in the territories can freely determine their political status. In 2013, the territory held a referendum in which 99 percent of the electorate voted for the Falkland Islands to remain a British Overseas Territory.

Quirno’s social media post came after the 2026 FIFA World Cup semi-finals on Wednesday, where Argentina’s national football team displayed the controversial banner “Las Malvinas son Argentinas” (The Falkland Islands are Argentine).

In response, Starmer’s spokesperson reiterated that the sovereignty of the Falkland Islands belongs to the UK. London has urged FIFA to launch an investigation into the displaying of the banner, saying that it was a violation of Article 34.3 of its regulations.

The territory’s Legislative Assembly also expressed disappointment at the display of the banner, saying it displayed “particular insensitivity” to the people of the Falklands. In a statement, lawmaker Michael Goss urged FIFA to “make good on their promise to keep politics out of sports” and sanction the behavior.

A FIFA spokesperson told Al Jazeera on Thursday that the organization has launched an independent disciplinary committee to consider further action. The team could face a fine of USD$5,000 to $20,000. Argentina’s football association previously faced a fine of 30,000 Swiss Francs for displaying the same banner in their international friendly against Slovenia, ahead of the 2014 World Cup.