German authorities said late Thursday that at least 58 people had likely died in massive storms and flooding in the country's west, an increase on the earlier toll of 45 dead.

The interior ministry in North Rhine-Westphalia state tallied four more bodies recovered, taking the region's toll to "at least 30", while neighbouring Rhineland-Palatinate said nine more deaths were likely on top of 19 already reported.

Unusually heavy rains also ravaged neighbouring Luxembourg, the Netherlands and Belgium, where another four people were reported dead.

Rhineland-Palatinate and North Rhine-Westphalia (NRW) states were the worst hit in Germany by the deluge, which has caused rivers to burst their banks and threatens to bring down more homes.

Desperate residents sought refuge on the roofs of their homes as helicopters circled above to rescue them from the rising waters.

Pensioner Annemarie Mueller, 65, looking out at her flooded garden and garage from her balcony, said her town of Mayen had been completely unprepared for the destruction.

"Nobody was expecting this, where did all this rain come from? It's crazy," she told AFP.

"It made such a loud noise and given how fast it came down we thought it would break the door down."

Chancellor Angela Merkel said she was "shocked" by the devastation and thanked the "tireless volunteers and emergency service workers" at the scene.

NRW leader Armin Laschet, who is running to succeed Merkel in September elections, cancelled a party meeting in Bavaria to survey the damage in his state, Germany's most populous.

"We will stand by the towns and people who've been affected," Laschet, clad in rubber boots, told reporters in the town of Hagen.

Go to higher floors

Four of the dead were in the municipality of Schuld south of Bonn where six houses were swept away by floods, a police spokesman in the city of Koblenz told AFP.

Several other bodies were recovered from flooded cellars while another eight people were reported dead in the district of Euskirchen.

The environment ministry in Rhineland-Palatinate warned it expected floodwaters on the Rhine and Moselle rivers to rise with more rainfall.

In NRW alone, 135,000 households were without power.

Emergency workers struggled to evacuate people in endangered buildings and two firemen were killed in the line of duty in the towns of Altena and Werdohl.

Police set up a crisis hotline for people to report missing loved ones and residents were asked to send in videos and photos that could help them in the search. 

Regional official Juergen Pfoehler urged people to stay home "and, if possible, go to higher floors" of their houses.

The German military deployed some 400 soldiers across the two affected states to assist in rescue efforts.

In the city of Leverkusen, a power outage triggered by the storms led to the evacuation of a hospital with 468 patients.

City authorities reported that after intensive care patients were moved to other facilities overnight, the other wards would have to be cleared in the course of the day.

Rarely experienced

Neighbouring Belgium has also seen several days of heavy rain that has caused rivers in the French-speaking region of Wallonia to burst their banks. Four were reported dead.

The provinces of Liege and Namur were especially affected, with the resort town of Spa completely flooded. In the town of Chaudfontaine, daily Le Soir reported that nearly 1,800 people had to evacuate.

"We have rarely experienced such intense flooding. You have to go back to 1998 to have experienced this," Chaudefontaine mayor Daniel Bacquelaine told RTL radio.

The country's Infrabel rail network said it was suspending services in the southern half of the country, given the risks to travel.

"It is indeed impossible to ensure the safe movement of trains for passengers or to have access to strategic areas for their staff," Transport Minister Georges Gilkinet told Belga news agency.

The southern Dutch province of Limburg, which is bordered by Germany and Belgium, also reported widespread damage with rising waters threatening to cut off the small city of Valkenburg west of Maastricht.

Local news footage showed small rivers of water flowing through the scenic city centre's streets and at least one old age home had been evacuated.

Officials also closed off several roads including the busy A2 highway, while fears remained that water from heavy rains in Germany and Belgium would push up river levels as it reached the Netherlands.

Meanwhile the Luxembourg government set up a crisis cell to respond to emergencies triggered by heavy rains overnight as Prime Minister Xavier Bettel reported "several homes" had been flooded and were "no longer inhabitable".