The Royal Navy has responded to a Spanish warship with its guns manned after it ordered commercial ships to leave British Gibraltar waters on Sunday, the territory's government said.
The warship's crew can be heard in an audio recording of a radio exchange telling vessels anchored at the Rock to "leave Spanish territorial waters".
Gibraltar Squadron deployed HMS Scimitar in response to the incident which was branded as "foolish" by a spokesman for Her Majesty's Government of Gibraltar.
The Royal Navy also responded by using a Rigid Hulled Inflatable Boat (RHIB).
The moment Spanish navy crew told vessels to 'leave Spanish territorial waters'
The spokesman said: "There is only nuisance value to these foolish games being played by those who don't accept unimpeachable British sovereignty over the waters around Gibraltar as recognised by the whole world in the United Nations Convention on the Law of the Sea.
"It seems there are still some in the Spanish Navy who think they can flout international law.
"This probably accounts for the state of extremism of some parts of the Spanish political spectrum these days."
The Gibraltar government accused the warship of trying to take "executive action" against the commercial boats, which were anchored on the eastern side of the Rock.
A crew member is heard in the recording asking the Spanish ship "to verify you are referring to our ship" because they are anchored in Gibraltar.
"We are not adrift, we are at anchor now," he says, before being told again to leave Spanish waters.
Commercial boats which were told to move were ordered to remain by the Gibraltar Port Authority.
A statement released by the Gibraltar government said: "The Royal Navy deployed a launch and a rigid-hulled inflatable boat to the scene.
"After being challenged by the Royal Navy, the Spanish warship sailed slowly along the Gibraltar coast with its weapons uncovered and manned."
The statement added the Gibraltar government "is verifying every aspect of the incident in order to ensure that appropriate action is taken as soon as possible".