As many as four tourists - including TV doctor Michael Mosley - have died in Greece in just a matter of days as a record heatwave threatens to plunge the Mediterranean state into crisis.

Holidaymakers looking to visit the country have been handed urgent warnings as temperatures have soared to nearly 50C - while three more people have gone missing alongside the tragic deaths.

The heatwave in the country - classed as temperatures higher than 38C for three days or more - is the earliest in its history, and has wreaked havoc from the capital Athens to its islands in the Aegean Sea.

After Mosley, 67, was found dead of natural causes on the island of Symi, three more tourists have died - and all three in Crete.

On June 5, a 67-year-old Dutchman died while crossing the Mylon gorge on the island - with local media pinning his demise on heart failure - while a 70-year-old French tourist collapsed and died on a beach in Sitia.

Then, on June 13, an 80-year-old man had left his hotel to walk by himself - and was found dead near an archaeological site near Malia.

Elsewhere in the country, search and rescue efforts are underway with authorities on the hunt for three more missing tourists - two of whom disappeared while out walking in the heat.

The head of the island of Samos's rescue team, Dimitris Katatzis, has warned tourists may not be wise to the risks presented by going outside amid the record heatwave.

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Katatzis said tourists were prone to "veering off track" while hiking, and lamented seeing foreigners "walking a trail in 41C without hats", adding: "It defies logic."

One city in Crete, Chania, had seen its thermometers record temperatures as high as a staggering 44.5C - and to compound its troubles, the area was also hit by a 3.7 magnitude earthquake at the same time.

Winds from North Africa have been blamed for the meteoric rise in temperatures - and data from forecasters MetDesk indicates Greece will see more of the same in the weeks to come.

Away from the Greek islands, historic tourist sites in Athens like the Acropolis were forced to close following reports of sightseers fainting while queueing for entry.

Authorities in the country have been forced to act - Greek emergency services have been sending out a "level three" heat alert, with warnings texted to locals urging them to stay at home if possible and avoid exercising or working outdoors.

Many primary schools and nurseries across the country have been closed to protect students from the heat, which has persisted despite being expected to recede on Saturday.

In Athens, tourists were pictured turning to drinking fountains to cool their heads and necks.

Elsewhere, firefighters who have already scrambled to put out several wildfires have been stationed on high alert with strong winds also expected to hit several parts of the country.