BERLIN (AFP) - German Finance Minister Wolfgang Schaeuble sparked a storm on Thursday with comments comparing the country's record refugee influx to an "avalanche", adding fuel to an already heated debate on migrants.

At a Berlin conference, Schaeuble told an audience of about 200 people: "I don't know if we are at the stage where the avalanche has hit the valley or whether it's at the stage where it's still at the upper end of the slope."

"An avalanche can be triggered by a careless skier on the slopes who moves a bit of snow," added Schaeuble, in what appeared to be a veiled reference to Chancellor Angela Merkel.

The conservative minister's comments sparked an outcry, and earned swift condemnation from Justice Minister Heiko Maas of the centre-left Social Democrats.

"People in need are not a natural disaster," Maas tweeted. "We should be level-headed in the debate over refugees and not add fuel to the fire."

Vice-Chancellor Sigmar Gabriel of the Social Democrats said: "I would not use such a comparison."

News site Spiegel Online called Schaeuble's description "a wrong and dangerous image".

"That is the speech of a rabble-rouser and xenophobe... a lapse," it wrote in a commentary.

The article also suggested Schaeuble, a straight-talking minister reviled in Greece for insisting on austerity in return for bailout loans, was targeting Merkel.

"Schaeuble is undermining Merkel's authority. Either he wants her to change course in her refugee policy. Or he wants her job," said the website.

Schaeuble belongs to Merkel's conservative Christian Democratic Union and is one of her most trusted and loyal allies.

But Merkel has come under fire within her conservative alliance over her open-door policy to refugees from Syria, as Germany struggles with a record number of new arrivals expected to reach a million this year.