Emergency workers in western German and Belgium are working to rescue hundreds of people in danger or still unaccounted for as the death toll from devastating floods rose to more than 120.

Authorities in the German state of Rhineland-Palatinate said 63 people had died there, including 12 residents of a care home for disabled people in the town of Sinzig who were surprised by a sudden rush of water from the nearby Ahr River.

In neighbouring North Rhine-Westphalia state officials put the death toll at 43, but warned the figure could rise.

German President Frank-Walter Steinmeier said he was “stunned” by the devastation and pledged support to the families of those killed and to cities and towns facing significant damage.

“In the hour of need, our country stands together,” he said. “It’s important that we show solidarity for those from whom the flood has taken everything.”

Rescuers sought to save people trapped in their homes in the town of Erftstadt, south west of Cologne.

Regional authorities said several people had died after their houses collapsed when the ground beneath them sank suddenly. Aerial photos showed what appeared to be a massive sinkhole.

“We managed to get 50 people out of their houses last night,” county administrator Frank Rock said. “We know of 15 people who still need to be rescued.”

He said authorities had no precise number for how many had died in the flash floods that turned roads into wild raging torrents, collapsing homes and overturning cars.

Authorities are still trying to account for hundreds of people listed as missing, but cautioned that the high number could be due to duplicated reports and difficulties reaching people because of disrupted roads and phone service.

Belgian interior minister Annelies Verlinden told the VRT network that the country’s official confirmed death toll had grown to 20, with 20 others missing.

Water levels on the Meuse Rriver that runs from Belgium into the Netherlands remains critical, and several dykes are at risk of collapsing, Ms Verlinden said.

Authorities in the southern Dutch town of Venlo evacuated 200 hospital patients due to the looming threat of flooding from the river.

Flash floods this week followed days of heavy rainfall in western Europe. Thousands of people remain homeless in Germany after their houses were destroyed or deemed at risk by authorities.

Malu Dreyer, governor of Rhineland-Palatinate state, said the disaster showed the need to speed up efforts to curb global warming, adding: “Climate change isn’t abstract any more. We are experiencing it up close and painfully.”

Mr Steinmeier echoed her calls, saying: “Only if we decisively take up the fight against climate change will we be able to limit the extreme weather conditions we are now experiencing.”

World Meteorological Organisation spokeswoman Clare Nullis said: “Some parts of western Europe… received up to two months of rainfall in the space of two days. What made it worse is that the soils were already saturated by previous rainfall.”

She said it was too soon to blame the floods and preceding heatwave on rising global temperatures, but added: “Climate change is already increasing the frequency of extreme events. And many single events have been shown to be made worse by global warming.”

Defence ministry spokesman Arne Collatz said the German military had deployed more than 850 troops to help with flood efforts, but the number is “rising significantly because the need is growing”.

Italy sent civil protection officials, firefighters and rescue dinghies to Belgium to help in the search for missing people.

In the southern Dutch province of Limburg, troops piled sandbags to strengthen a 0.7-mile stretch of dyke along the Maas River and police helped evacuate low-lying neighbourhoods.

Caretaker Dutch prime minister Mark Rutte said the government was officially declaring flood-hit regions a disaster area, meaning businesses and residents are eligible for compensation.

King Willem-Alexander visited the region on Thursday night and called the scenes “heart-breaking”.

Meanwhile, sustained rainfall in Switzerland caused several rivers and lakes to burst their banks.

Public broadcaster SRF reported that a flash flood swept away cars, flooded basements and destroyed small bridges in the northern villages of Schleitheim und Beggingen.