German emergency responders were on Friday still searching for hundreds of missing people after the worst floods in living memory killed 120 people in the country's west.

At least 120 people have died and hundreds more in western Europe are unaccounted for after some of the worst flooding in decades.

Record rainfall caused rivers to burst their banks, devastating the region.

In Germany, where the death toll now stands at over 100, Chancellor Angela Merkel called for a determined battle against climate change.

At least 20 people have died in Belgium. The Netherlands, Luxembourg and Switzerland are also affected.

Many factors contribute to flooding, but a warming atmosphere caused by climate change makes extreme rainfall more likely.

The world has already warmed by about 1.2C since the industrial era began and temperatures will keep rising unless governments around the world make steep cuts to emissions.

"I fear that we will only see the full extent of the disaster in the coming days," Chancellor Angela Merkel said from Washington, where she met with President Joe Biden.

Catching residents of several regions unaware and leaving destruction and despair in their wake, the masses of water were dubbed the "flood of death" by top-selling daily Bild.

Neighbouring Belgium counted at least 18 dead, while Luxembourg and the Netherlands were also severely affected by the torrents of water, with thousands evacuated in the city of Maastricht.

Some 15,000 police, soldiers and emergency service workers are searching for hundreds of people reported missing.

Helicopters are being used to rescue people from rooftops and tanks have cleared roads of fallen trees and debris.

Chancellor Angela Merkel has pledged full support for the victims after "a day of worry and despair".