Latvian authorities on Sunday urged residents of certain central areas to evacuate their homes in response to the worst flooding the Baltic state has seen in decades.
"It will be near impossible to get you out from among the ice cold sludge once it rushes into your homes," Raivis Ragainis, mayor of the city of Jekabpils, warned on local radio.
Particularly exposed are Jekabpils and the town of Plavinas and surrounding areas, where the flow of the Daugava river has been blocked by pack ice that drifted in from Belarus.
"Chunks of ice and torrents of ice-cold water rapidly took over our city," Jekabpils resident Maris Kodols told AFP.
"These are the worst floods since 1981," he said, adding that current water levels are just five centimetres (two inches) below that year's all-time record.
A new dam was built 10 years ago as a precautionary measure, but it began to crumble Saturday under the pressure of the ice.
Several excavators were deployed to strengthen the dam with fresh piles of sandbags on Sunday.
"The dam has survived so far, as we are constantly strengthening it, but the situation remains tense," Ragainis, the mayor, said.
"There is no guarantee that it will withstand the extreme circumstances," he added.
Rescuers had deployed floating tanks -- a kind of amphibious vehicle -- to evacuate residents, though the majority had so far chosen to stay put.
"Thank God nobody has drowned or been injured so far," army captain Aleksands Cviguns, head of the military rescue operation, told AFP.
"Today our floating tank visiting five remote farms, evacuating people and delivering food and supplies to those who are staying," he added.
Prime Minister Krisjanis Karins and President Egils Levits organised a crisis management meeting in the capital Riga.