It's a spectacle that has some visitors tickled pink - the Australian city of Melbourne's Westgate Park lake has turned from blue to pink.

Parks Victoria, which oversees the lake, said that while it gets comments that the lake looks like an industrial accident of pink paint, the process is a natural one.

The agency's chief conservation scientist Mark Norman was quoted by Agence France-Presse as saying yesterday that the spectacle was the result of green algae at the bottom of the lake responding to high levels of salt and changing colour.

"The bright pink lake pops up most summers and is made by a native single-celled plant known as Dunalliela that responds to extreme levels of salt in this lake," he said, adding that hot weather makes the salt concentrate further.

Parks Victoria said on its Facebook page that the lake is expected to return to its normal colour towards winter, when the weather cools and rainfall increases. It encouraged people to "enjoy the views", but warned them not to come into contact with the water.

The sight is made for social media. Family website Mamma Knows West asked on Twitter: "Did someone spill their strawberry milkshake?"