The British government on Sunday accused Spain of violating its sovereignty over Gibraltar, saying Spanish state vessels had repeatedly and unlawfully entered its territorial waters without notifying it.

"These repeated incursions into British Gibraltar territorial waters are a clear violation of UK sovereignty by another EU country and we will be raising this as a matter of urgency with the Spanish authorities," Hugo Swire, a Foreign Office minister, said in a statement.

No one from Spain's Foreign Office was immediately available to comment.

The incident is the latest in a long line of diplomatic spats between Britain and Spain over the territory, which was ceded to Britain about 300 years ago but which Spanish authorities now want to reclaim.

Britain, which runs the rocky outcrop off Spain's southern coast, said it believed the offending Spanish vessels had been in pursuit of other boats which may have been committing unspecified crimes.

But Swire said he still deemed it "completely unacceptable and unlawful" under the international law of the sea for Spain to enter Gibraltar's territorial waters without notification.