Hundreds of swimmers on Spain's holiday beaches have been stung by swarms of jellyfish that have swept along the Costa Blanca.

At least 700 people have complained of being stung since Sunday - 380 alone on Tuesday.

Normally just a handful of swimmers are stung every day.

The jellyfish are tiny and invisible, meaning it is difficult to warn bathers of their presence.

"In the five or six years I have been in this job, I have never seen anything like this," said Juan Carlos Castellanos, of Elche's city tourism department.

Officials have blamed strong currents for sweeping the jellyfish onto beaches.

In the north, it is the much-feared Portuguese Man of War that has been plaguing beaches in the northern areas of Cantabria and Basque.

At least 300 swimmers have been stung in the last three weeks - the creature's three-foot tentacles carry a venom that causes intense pain.

Despite the spate of stings, officials say this summer has been quiet on the jellyfish front.

But scientists say jellyfish numbers could rise due to global warming and intensive fishing off the Spanish coast that kills its natural predators, such as tuna and swordfish.

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