Large numbers of potentially fatal Portuguese man-of-war have washed up on a Cornish beach, prompting its closure.

RNLI lifeguards erected do not swim red flags at Perranporth beach earlier because of the "unusually large number" of the creatures.

The jellyfish-like organisms, which have long purple tentacles, have also been seen in Wales this month, says the Marine Conservation Society (MCS).

With mild sea temperatures of 16C there were fears of swimmers being stung.

The RNLI said it placed red flags at Perranporth beach between 10:00 and 13:30 BST to signal that the water was out of bounds, while lifeguards took advice on the level of danger to beachgoers.

More on the man-of-war sightings and other stories from Cornwall

Man-of-war were spotted at Newgale, Pembrokeshire, on 8 September and the next day on beaches near the holiday destination of Newquay.

Image copyrightRACHEL WYATT

They have also been seen at Porthmelon Beach on the Isles of Scilly and on the Cornish beaches of Portheras Cove and Summerleaze, Widemouth, Perranporth, Hayle, Holywell Bay and Praa Sands.

Six were also reported at Gwithian.

Dr Peter Richardson from the MCS said a man-of-war's tentacles, which are usually about 10m (30ft) long, "deliver an agonising and potentially lethal sting".

"They are very pretty and look like partially deflated balloons with ribbons but picking one up could be very nasty," he said.

The man-of-war retain their sting when they are wet, even if they look dead, he warned.

He advised anyone who was stung to get the tentacles away from the body as soon as possible.