Norway faced more floods and evacuations as rivers swelled above their banks to their highest levels in decades after heavy rain that meteorologists said resulted from unusual weather patterns, writes Reuters.

More than 4,000 people are currently evacuated from their homes in southern Norway, officials said, almost half of them in the town of Hoenefoss some 40 km north-west of Oslo, an increase from around 3,000 people on Wednesday.

Strong winds, intense rain and landslides hit the Nordic region earlier this week, knocking out power lines and bringing public transport to a standstill.

On Wednesday, a hydroelectric river dam collapsed as water forced its way through, and earlier this week a train derailed in neighbouring Sweden when a railway embankment was washed away by floods. Main roads were closed and train services suspended across wide parts of southern Norway on Thursday and authorities warned of more flooding ahead, even though the rain had stopped, as the water flows towards lower-lying coastal regions.

Unlike most precipitation to hit Norway, which originates from the west, the latest weather approached from the east when two low pressure systems merged and intensified as they moved towards the Nordic region, the NMI said.

According to the institute, data shows that precipitation in Norway has increased by around 18% over the last 100 years, with the biggest rise taking place in the last 30-40 years.