Police in Spain have been accused of committing an “outrageous” violation of British sovereignty after Spanish ships and helicopters crossed into British waters off Gibraltar as they sought to apprehend fleeing suspects, British news outlets reported Sunday. Gibraltar's authorities said Spain should have sought their government's assistance in seeking suspects once they crossed into Gibraltar's territory, and said failure to do so resulted in the escape of a suspected drug smuggler.

“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," Hugo Swire, a minister for Britain's foreign office, said. “These repeated incursions into British Gibraltar territorial waters are a clear violation of U.K. sovereignty by another [European Union] country and we will be raising this as a matter of urgency with the Spanish authorities.”

In one incident, Spanish authorities were believed to have been pursuing drug smugglers who were suspected of dumping drugs off the side of a high-speed inflatable boat, the BBC reported. In a separate incident, Spanish police reportedly flew a helicopter over a beach, an act that the Gibraltar government lambasted as "extremely dangerous." Spanish authorities also reportedly boarded a boat within British waters and questioned its crew.

Gibraltar's government said it was "appalled" by the territorial breaches. "I am sure I am speaking for the whole of Gibraltar when I say that we consider this has been a serious and unnecessary failure on the part of the Spanish [police], which has had outrageous consequences in respect of the violation of our sovereignty," Fabian Picardo, chief minister of Gibraltar, said, the BBC reported.

Gibraltar has been under the British crown for more than 300 years, but tensions with Spain resurface occasionally as the Spanish government continues to insist the territory should again come under its control. Gibraltarians overwhelmingly reject Spanish claims over their land, which sits in the southern end of the Iberian Peninsula. Last year, the BBC reported several minor collisions between Spanish and Gibraltar authorities over similar territorial disputes.