"It seems that the mountainous region of Magnesia was hit by 600 to 800 mm of rain in 24 hours", said Dimitris Ziakopoulos, vice-president of the Crisis Management Studies Center of the climate crisis ministry.

It was, he told reporters in Athens, "an unprecedented phenomenon for the country's meteorological data", which dates back to 1955.

The amount totals more than an average year's rainfall in the region in just one day, according to data from the Greek Meteorological Service.

The storm, dubbed "Daniel" by Greek meteorologists, has been battering the country since Monday, mainly affecting the central Magnesia region and its capital city Volos, 300 kilometres (185 miles) north of Athens.

According to the Greek fire brigade, two people were killed and four were missing following the torrential rains.

The storms were forecast to continue until at least Thursday afternoon and could also affect Athens, the Greek capital.

Police have banned travel to Volos, certain villages on Pelion and the nearby island of Skiathos.

Skiathos airport resumed operation on Wednesday, but the port of Volos was still not working, said Greek officials.

On Wednesday police issued traffic warnings for the cities of Trikala and Karditsa, in central Greece, as the rainstorm was expected to intensify again later on Wednesday.