As it passed into territorial waters the Spanish national anthem could be heard over a maritime communications frequency. Gibraltar, located on the southern coast of Spain, has been a British Overseas Territory since 1713, when Spain ceded it to the United Kingdom under The Treaty of Utrecht.

Axar.az reports citing foreign media that, a vast Spanish patrol boat was chased away from the coast of Gibraltar by a small Royal Navy vessel January 5 after it encroached on British-controlled waters during an exercise off the coast Gibraltar.

The tiny HMS Sabre was involved in manoeuvres with a Royal Navy RHIB, when the Spanish vessel — the Tornado — sailed into the training drill, where it remained for two hours.

In the exercise — widely advertised in advance by the Gibraltar authorities — ships were warned a ''high speed manoeuvring and blank firing'' would take place, and passing ships who needed to contact the Royal Navy vessels involved were advised to use Channel 16 — which the Spanish did, to broadcast the country's national anthem.

Gibraltar has been a British territory for over three centuries — since the June 2016 Brexit vote, it has become a hotly disputed issue between the two NATO member states, despite the territory voting overwhelmingly to remain a British overseas territory in a 2002 referendum, with 99 percent choosing to align solely with the UK rather than share sovereignty with Spain.

The incursion came mere days after the European Union enraged Whitehall by dubbing Gibraltar a "colony of the British crown" in a document guaranteeing visa-free travel for UK citizens after Brexit.

"We can confirm an incursion by the Spanish navy occurred. As with all incursions, the Royal Navy challenged the vessel. When challenged, the Spanish navy vessel subsequently left British Gibraltar Territorial Waters. Incursions are a violation of sovereignty, not a threat to it. We have no doubt about our sovereignty over Gibraltar. The UK will never enter into arrangements under which the people of Gibraltar would pass under the sovereignty of another state against their wishes, nor enter into a process of sovereignty negotiations with which Gibraltar is not content", the Foreign & Commonwealth Office said in a statement.