Malta's famous Azure Window rock formation has collapsed into the sea in what the country's prime minister described as a "heartbreaking event".

Known in Malta as Tieqa tad-Dwerja, the Azure Window arched over blue seas popular with divers and featured in countless tourism brochures.

It collapsed along with the its flanking stacks as Malta was hit by rough seas and stormy weather.

Several people shared their memories of the limestone arch on social media.

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.

Gozo resident Roger Chessell went to the coastline in the morning to take pictures and told the Times of Malta: "There was a big raging sea beneath the Azure Window.

"Suddenly, the arch collapsed into the sea with a loud whoomph, throwing up a huge spray. By the time the spray had faded, the stack had gone too."

Prime Minister Joseph Muscat said in a Tweet that the famous Mediterranean landmark had always faced destruction because of natural corrosion.