The Greek culture ministry shut the world-renowned site from 1:00 to 5:00 pm (1000 to 1400 GMT) "for the safety of workers and visitors, owing to high temperatures."

The four-day heatwave confirmed by meteorologists began Sunday is the second to grip Greece since late June.

The national weather service EMY said temperatures in Athens in the afternoon had reached 37 degrees Celsius (98.6 Fahrenheit), and 40C in central Greece.

Similar temperatures are expected on Wednesday, before dropping Thursday.

To protect outdoor workers, the labour ministry decreed a work stoppage from 12:00 to 5:00 pm in various parts of the country, including several islands.

The stoppage mainly affected construction work and delivery riders.

"Days with a heatwave make my job more difficult," cycle-riding courier Michalis Keskinidis told AFP.

"We drink a lot of water to protect ourselves from the heat, combined with electrolytes, and take breaks whenever possible," the 43-year-old said.

The 2,500-year-old Acropolis, built on a rock overlooking the capital that offers little shade, draws tens of thousands of visitors daily.

Last year it recorded some 4.5 million visitors, an increase of over 15 percent compared to 2023.

Officials had been forced to order similar shutdowns in the past two years in heatwave conditions.

Southern and western Europe experienced an early heatwave at the end of June, affecting France, Belgium, the Netherlands, Italy, Spain, and Portugal.

- Risk of fire, storms -

The Greek civil protection authority has warned of high fire risk in the greater Athens area, in central Greece and the Peloponnese peninsula on Wednesday.

Greece's fire department has been dealing with up to 50 fires daily, the head of the Greek fire service officers' union Constantinos Tsigkas told state TV ERT.

Elsewhere, Serbia's hydrometeorological service RHMZ warned that weather conditions could fuel more fires, after 620 fires were recorded Monday.

But there are also thunderstorms expected in Serbia's northern Vojvodina region, as well as in western and central areas.

RHMZ has also warned of the possibility of hail and hurricane-force gusts of wind.

Croatia has already felt the impact of storms since Monday, with several of the country's regions affected.

Two people were injured and hospitalised in Vinkovci after a storm knocked down a power line on a family house near the eastern town, police said.

The authorities said they had taken dozens of calls over wind-related emergencies including trees blocking roads, damaged roofs and power failures.

On Tuesday, heavy rain and gale-force winds flooded roads, knocked down trees and caused power outages at the Croatian port town of Split, the state-run HRT broadcaster reported.

At the town's port, a ferry broke its moorings and hit a catamaran and a tourist excursion boat, sinking the latter.

There was similar trouble further north, with storms raging in Hungary and Slovakia.

In Budapest, strong winds damaged roofs, felled trees onto roads and downed power lines on Monday, with the national meteorological service HungaroMet measuring winds up to 137 kilometres (85 miles) per hour locally.

Rail traffic was severely disrupted across Hungary with full restoration of services potentially requiring weeks, according to Construction and Transport Minister Janos Lazar.

In Slovakia, gale-force winds caused power outages and blew off the roof of a block of flats in the eastern town of Gelnica and fallen trees disrupted road and railway transport across the region.

The country's weather service SHMU has issued a storm warning with heavy rain, wind and hail for Tuesday, mainly for central and eastern Slovakia.

burs-yap/jph/giv