Following a day of frantic rescue efforts and orders to evacuate towns rapidly filling with water unloosed by violent storms, the German authorities said late Thursday that after confirming scores of deaths, they were unable to account for at least 1,300 people.

That staggering figure was announced after swift-moving water from swollen rivers surged through cities and villages in two western German states, where news outlets said more than 80 people were known to have died in the hardest-hit regions and other fatalities were expected.

With communication badly hampered, the authorities were hoping that the missing people were safe, if unreachable. But the storms and the floods have already proved deadly.

At least 11 more people were reported to have died in Belgium, according to authorities who also ordered inhabitants of downtown Liège to evacuate as the Meuse River, which flows through its center, overflowed its banks.

The storms and resulting high water also battered neighboring Switzerland, the Netherlands and Luxembourg as a slow-moving weather system threatened to dump even more rain on the inundated region overnight and into Friday.

The devastation caused by the severe weather came just days after the European Union announced an ambitious blueprint to pivot away from fossil fuels over the next nine years, as part of plans to make the 27-country bloc carbon-neutral by 2050. Environmental activists and politicians were quick to draw parallels between the flooding and the effects of climate change.But the immediate focus on Thursday remained the rescue efforts, with hundreds of firefighters, emergency responders and soldiers working to save people from the upper floors and rooftops of their homes, fill sandbags to stem the rising water and search for the missing.

One of the most heavily hit regions was Germany’s Ahrweiler district, where flash floods surged through the village of Schuld, washing away six houses and leaving several more on the verge of collapse. The police said at least 50 people had died in Ahrweiler district.

With so many people unaccounted for, the district authority said late Thursday that the number of dead was expected to climb. “Given the complexity of the level of damage, it is not possible at this time to make a final assessment of the situation,” it said in a statement.

“We have no exact numbers of dead, but can say that we have many people who have become victims of this flood,” Armin Laschet, the governor of North Rhine-Westphalia, one of the hardest-hit states in Germany, told reporters.

“Many people lost everything that they own after the mud flowed into their homes,” said Mr. Laschet, who is running to replace Angela Merkel as chancellor in national elections on Sept. 26.