Two men in a boat shouted anti-British slogans and cursed the Queen, accusing her of murder.

They threatened to "teach the Prince a lesson" before a Royal bodyguard persuaded them to leave.

A spokeswoman for St James' Palace said: "We can confirm that the occupants of a boat in the Mediterranean Sea approached and tried to speak to two members of the Royal Family who were nearby.

Camilla is holidaying with the Prince

"A protection officer spoke to them and they moved away."

The incident happened on Thursday during the Prince's holiday with sons Princes William and Harry and his partner Camilla Parker Bowles.

The Royals were cruising with friends in the Mediterranean on board the luxury yacht, The Alexander, owned by Greek shipping magnate John Latsis.

The Prince and the Queen's cousin, Princess Alexandra, had gone off in a small boat for a swim, accompanied by police bodyguard Inspector Peter Brown in a separate high-speed dinghy.

As the protesters approached the Prince, Inspector Brown, 41, intercepted them and managed to defuse the situation.

Princes William, 17, and Harry, 15, were relaxing on board the yacht unaware of the incident.

It is not clear what sparked the incident. Six years ago, the Queen faced bomb threats from Greek Cypriot extremists when she visited Cyprus.

Some activists there hold the her personally responsible for the execution in the 1950s of nine fighters arrested by the British during the struggle for independence on Cyprus.