Devastating floods triggered by torrential rains have caused the death of at least three people in Slovenia, with estimated damage of 500 million euros ($550m).

Prime Minister Robert Golob said on Saturday that floods on Thursday and Friday were “the biggest natural disaster” in the small Alpine nation’s history.

Golob said road and energy infrastructure were hit particularly hard, as well as hundreds of homes and other buildings. Thousands of people have been forced to evacuate their homes and many had to be rescued by helicopters or firefighters in boats.

Slovenia’s army has joined the relief effort, with troops reaching cut-off areas in the north to help.

Two-thirds of the territory in the country, home to two million people, were affected, the prime minister said.

Among those who died were two Dutch climbers on Friday in the mountains near Kranj, presumably as a result of being struck by lightning, Slovenia’s STA news agency reported citing police.

Also on Friday, a woman died due to flooding in the town of Kamnik, 20km (12.5 miles) north of the capital, Ljubljana, according to the report.

European Commission President Ursula von der Leyen assured Slovenia of the union’s help. The damage in Slovenia was “heartbreaking”, she tweeted.

In Dravograd, near the border with Austria, 110 people, including 30 tourists, had to be brought to safety after a landslide Saturday.

The town, which lies at the confluence of three rivers – Drava, Meze and Mislinje – was at risk of another landslide.