COPENHAGEN, Denmark (AP) -- Days of heavy rain triggered landslides and flooding in mountainous southern Norway, where authorities said Wednesday they were considering blowing up a dam at risk of bursting to prevent downstream communities from getting deluged.
The Glåma, Norway's longest and most voluminous river, is dammed at the the Braskereidfoss hydroelectric power plant, which was under water and out of operation. Police said a controlled explosion before the dam fails would allow officials to control the flow of water.
"When there is so much water, we can perhaps imagine, in the worst case, a kind of tidal wave coming sailing down the river," police spokeswoman Merete Hjertø told Norwegian broadcaster NRK.
Police in southern Norway said more than 600 people were evacuated in a region north of Oslo overnight and said the situation there was "unclear and chaotic." The Norwegian Public Roads Administration said Wednesday that all main roads between Oslo and Trondheim, Norway's third-largest city, were closed.
"We are in a crisis situation of national dimensions," Innlandet country Mayor Aud Hove said. "People are isolated in several local communities, and the emergency services risk not being able to reach people who need help."
More heavy rain was expected over southern Norway and central Sweden.
Storm Hans has battered parts of Scandinavia and the Baltics for several days, causing rivers to overflow, damaging roads and injuring people with falling branches. In Sweden and Norway, sheds, small houses and mobile homes floated in rivers or were carried away by strong sea currents.
Erik Hojgard-Olsen, a meteorologist with the Swedish Meteorological and Hydrological Institute, was quoted as saying by the Aftonbladet newspaper that the weather was unusual for this time of year.
"It is exceptional to have such a low pressure (system) as Hans, which has brought so much rain for several days in a row," he said. "Especially for being a summer month, it has lasted a long time."
Large parts of the harbor in Goteborg, Sweden's second-largest city, was under water. The meteorological institute on Wednesday its red-level warning for the country's west coast, saying "very large amounts of rain causing extremely high flows in streams" could be expected.
The Norwegian Water Resources and Energy Directorate upgraded its warning for floods, landslides and landslides from orange to red for parts of southern Norway. The directorate said record high flood levels were recorded in several places in the Drammensvassdraget, a drainage basin west of Oslo, the capital.
Erik Holmqvist, a senior engineer at the agency, said four lakes. including Randsfjorden, Norway's 4th- largest one, were particularly vulnerable to flooding.
"We have to go all the way back to 1910 to get the same forecasts for the Randsfjorden," Holmqvist told the VG newswpaper.
The Norwegian Meteorological Institute issued its highest extreme weather warning due to heavy rain.
"This is a very serious situation that can lead to extensive consequences and damage," it said.