The British Foreign Office has accused Spain of a "clear violation of the international law" by entering UK territorial waters on several occasions over the past two days.
The incidents occurred while Spanish police were chasing criminals who tried to escape to Gilbraltar, which is under British control. Despite this, UK Foreign Minister Hugo Swire says that the incursions are "completely unacceptable."
"We understand that the Spanish were in pursuit of vessels who may have been committing crimes. However it is completely unacceptable and unlawful under the international law of the sea to enter our waters without notifying us," Swire added.