'Auf Wiedersehen!'

From chants of "goodbye" to stunned silence, Germany fans reacted with dismay to their defending champions' humiliating World Cup exit Wednesday after a first-round loss commentators called a "historic disgrace".

"Our World Cup nightmare has come true," screamed the Bild daily.

Even before the final whistle blew in Russia's Kazan Arena, supporters in Berlin had begun leaving the city's so-called fan mile, disappointed by Germany's lacklustre performance against South Korea in a match heavy with missed opportunities.

Those who remained applauded sarcastically when South Korea's Son Heung-min scored a late second goal into an empty net.

Calls of "Raus (Out)" and "Auf Wiedersehen (goodbye)" rang out from the fan zone as the weight of the 2-0 loss sunk in.

"These aren't world champions, they didn't fight at all," fumed 27-year-old Oliver Fischer, wearing a Germany jersey.

"We absolutely deserve to be out. We had no fight, no courage, no ideas!"

Others erupted into tears and buried their heads in their hands as a sense of disbelief spread through the crowd at Germany's largest public viewing area.

"Speechless," read a one-word tweet on the German team's official Twitter account, summing up the national mood.

The defeat was the first time four-time champions Germany have been knocked out of the World Cup group stages since 1938.

The country now joins a small but unlucky club of title defenders who crashed out of the first round at their next World Cup, a feat last achieved by Spain at the last World Cup in 2014.

"It's a historic disgrace," Der Spiegel weekly said, decrying Germany's "weak game" against a plucky South Korea.

Germany had needed a clear win to move into the last 16, but a series of wasted chances saw the team finish last in Group F.

Chancellor Angela Merkel, speaking at a Berlin event about artificial intelligence, expressed her sadness in a "discussion" with a robot named Sophia, who noted how successful the German team had been in the past.

Merkel responded: "Yes, that's true seen over a long timeframe. But tonight we're all very sad."

Her spokesman also shared the shock of a nation in a tweet. "Not our World Cup - How sad! There will be other tournaments where we can cheer again," Steffen Seibert wrote.

Former Germany goalkeeper Oliver Kahn, who was a losing World Cup finalist in 2002, said: "The national jersey must feel like it weighs a million tonnes to the players right now."

But others were less generous.

"This is a shock for German football. There's going to be a sea-change... No one expected this," said seasoned commentator Bela Rety from public broadcaster ZDF, speculating about the future of head coach Joachim Loew.

Former Germany star Mario Basler slammed the national team's sub-par performance. "If you can't win this game, you don't belong in the final 16," he tweeted.

Sports website Kicker dubbed the match a "historic debacle" that called for a radical rethink. Continuing with Loew is "hardly imaginable", it wrote.

Despite the heartache, not all Germany fans despaired.

"We were too slow, we deserved to lose," admitted Laura Kabinsky, who watched the match at Berlin's fan mile. But the 20-year-old student was determined to look on the bright side.

"Let's see if we can do better at the European Championships in two years' time," she smiled.