Valletta: A rock structure in the form of an arch which had featured in countless Malta tourism brochures and The Game of Thrones has collapsed into the sea in what Prime Minister Joseph Muscat described as a "heartbreaking event".

Geologists had long warned that the structure, on the north-western coast of the small island of Gozo, was eroding fast and the authorities had banned visitors from walking on top of it.

The structure, known as the Azure Window because it arched over blue seas popular with divers, collapsed on Wednesday as Malta was hit by rough seas and stormy weather.

Prime Minister Muscat said in a tweet that the famous Mediterranean landmark had always faced destruction because of natural corrosion. "That sad day has arrived," he wrote.