The marine invertebrates, which look similar to jellyfish, have all been on Guernsey’s west coast, between Pezeries and Chouet.

The Portuguese man o’ war is not a true jellyfish, but a colony of tiny stinging organisms known as hydrozoans.

‘Their tentacles may be as long as 50 metres, though are more usually around nine metres,’ an ACLMS spokesman has said.

‘They can deliver a painful sting, which can, on rare occasions, be fatal.

‘The specimens found so far in Guernsey have not had long tentacles still attached, and the floats have all been small enough to fit in the palm of a small adult hand. Some individuals have retained their bright blue and mauve colouration, whereas others have appeared largely colourless.’

In the past two weeks there have also been a number of Portuguese man o’ war sightings around the coast of Cornwall, Wales, Ireland, the Isles of Scilly, and Brittany.

‘It is thought that they have been blown to Western Europe by strong and persistent south-westerly winds,’ the spokesman said.

Agriculture, Countryside and Land Management Services asks that members of the public report any unusual sightings by phoning 234567 or emailing aclms@gov.gg.

It advises that beachgoers do not touch any jellyfish they may find on the beach, and that dogs are kept on leads. If members of the public wish to swim in the sea, they are advised to remain vigilant, and if possible to wear a long-sleeved wetsuit.

If anyone believes they have been stung, the NHS website recommends removing any remaining tentacles, bathing the area with seawater to help neutralise it, and immersing the area in hot water to help relieve the pain. If pain is long lasting, other symptoms develop or the area becomes infected, further medical assistance should be sought.