The sun shone red and the sky darkened to a foreboding orange and brown across parts of Britain on Monday, as a storm swept air and dust in from southern Europe.

Social media users shared pictures of ominous-looking clouds blocking out the sun, prompting London's Science Museum to joke on Twitter: "It's not the apocalypse!"

Many people expressed unease at the phenomenon, while others remarked it looked like something out of a science fiction movie -- with one wit predicting an alien invasion.

The prospect of the impending end of the world also drew inevitable comparisons with Britain's increasingly tortured withdrawal from the EU.

"Huh, turns out Remoaners were right... #BrexitApocalpyse #YellowSky," tweeted one of the leading Brexit campaign groups, Leave.EU.

Met Office forecaster Grahame Madge said the unusual effect was caused by Ophelia, the hurricane now downgraded to a violent storm which battered Ireland on Monday.

"On the eastern side of the low pressure system air is coming up in the southern direction. Air is being pulled from southern Europe and Africa and that air contains a lot of dust," he said.

"So it's most likely the appearance of sunset at midday is caused by the particles scattering the light and giving the appearance of a red sun.

"It's certainly spectacular at the moment and quite a talking point, we've had a lot of calls about it."

Source: AFP