An Austrian couple on honeymoon is missing in Greece after torrential rains swept away the house they were staying in.
Emergency services have told the BBC they are searching for the couple and several other missing people.
People in central Greece were trapped on the roofs of their houses after floods set whole villages under water.
More than a dozen people are now known to have died since Storm Daniel hit Greece, Turkey and Bulgaria this week.
The Austrian couple reportedly decided to shelter inside the bungalow they had rented for their honeymoon as heavy rainfall swept central Greece.
But the house in the beach resort of Potistika, near Mount Pelion, was then washed away by flash floods late on Tuesday, reports said.
The Greek Fire brigade said it had a team in the area searching for missing people, including the Austrian couple.
Some Greek regions received up to 800mm (31.5 inches) of rain in recent days – more than normally seen in a year.
The Karditsa plain central Greece was described as having turned into a “lake”, with villages around Palamas drowned in water.
The mayor of Palamas, Giorgos Sakellariou, made a dramatic appeal for help on Greek TV, saying people were stranded in their homes and facing immediate danger.
“The situation in Palamas is tragic,” he was quoted as telling Skai TV.
“The water is 1.5m, 2m high. In the house I’m in, we’re trapped. It’s 1.5m (4.9 feet) deep at least. People are trapped in their houses. We will have people drowning.”
The extreme weather also hit Athens and the island of Skiathos as well as coastal areas around Volos and Pelion.
Prime Minister Kyriakos Mitsotakis cancelled a big government engagement planned for the weekend as the crisis escalated.
Storm Daniel has been hitting Greece, Turkey and Bulgaria since Monday, with more than a dozen people known to have died.