Vehicles wait to enter the British territory of Gibraltar at its border with Spain

A Spanish warship disrupted a Royal Navy training exercise after entering the waters of Gibraltar, the latest in a series of diplomatic incidents between Britain and Spain over the disputed territory.

A British military parachute exercise was taking place when the Spanish SPS Vigia approached the landing zone for the soldiers, forcing the exercise to be suspended by military chiefs.

The Gibraltar Squadron, the Royal Navy's submarine parachute assistance group, were being shadowed by HMS Sabre, which had to break away from the exercise and shadow the intruding Spanish vessel.

According to the Gibraltar Chronicle, HMS Sabre issued warnings to the Spanish ship but it only departed after declaring that it was in Spanish waters and not violating the waters of Gibraltar.

"There was a slight delay until the safety boat came back," said a Royal Navy spokesman.

Tensions have escalated over the disputed territory following the construction of an artificial reef around Gibraltar last year that the Spanish government claim is affecting the country's fishermen.

In retaliation, Spain has imposed stricter border controls between the territory and the mainland, leading to huge queues for visitors.

A Spanish ambassador was summoned by the Foreign Office after numerous incursions by Spanish vessels into Gibraltarian waters.

Last year, a British diplomatic bag was opened by a Spanish border guard, incurring condemnation from the Foreign Office who claimed the opening of the bag was a breach of international diplomatic protocols.

UK Foreign Secretary William Hague described the November incident as the "latest unacceptable incursion into British Gibraltar territorial waters".