The number of refugees seeking asylum in Germany could surge to 750,000 this year, according to reports citing official projections.
The government in Berlin had earlier forecast that 450,000 asylum seekers could arrive in 2015, but is now set to increase that to 650,000 or higher.
Germany has seen a wave of migration from Syria and the Balkans.
UN High Commissioner for Refugees Antonio Guterres said more countries in Europe should share the burden.
“It is unsustainable in the long run that only two EU countries, Germany and Sweden, take in the majority of refugees,” he told German daily Die Welt.
Up to 80,000 people, many of them Syrians, are expected to seek asylum in Sweden this year, but Germany has become the most popular destination.
Helping the refugees – by Jenny Hill, BBC Berlin correspondent
Squatting on a kerb, Barakat smiles as a volunteer hands his young son and daughter some second-hand clothes.
The family are Yazidis and fled Iraq. “They were killing all the women – what were we supposed to do?”
Nearby, hundreds of people queue outside a grey concrete building. Every so often an official comes out and shouts instructions through a megaphone.
This is Berlin’s reception centre, where refugees come to register for housing and benefits. But it is volunteers who provide food, water, clothing and medical help. A doctor holds a makeshift surgery in a tent.
“It shouldn’t be volunteers doing this,” he says. “But the authorities never expected this many people to arrive so suddenly.”
As I leave, I pass an old lady slowly pushing a trolley towards the centre. “I’ve come to donate clothes,” she tells me. “Why wouldn’t you help these people?”
Pressure on Greece
More than 240,000 migrants have crossed the Mediterranean already this year, arriving on the shores of Greece and Italy before travelling on to other destinations.
In the past week alone, 21,000 migrants have arrived in Greece, according to the United Nations.
Germany’s latest projected figures were due to be confirmed by Interior Minister Thomas de Maiziere on Wednesday and Handelsblatt reported that the number of refugees seeking accommodation around the country was surging.
Last month alone, 5,700 people applied for asylum in the northern city of Hamburg and 7,065 in the south-western state of Baden-Wuerttemberg.
“I would have to build a block of flats every day to accommodate them”, Stuttgart Integration Minister Bilkay Oeney told Handelsblatt.
The numbers are far higher than the record 438,000 asylum applications in 1992 during the Bosnian crisis.
Few arrivals from Balkan countries such as Albania or Kosovo are granted asylum in Germany and the government in Berlin is currently considering measures aimed at discouraging Balkan migrants from arriving.
German towns have been housing refugees in tent cities and converted gyms, but as tensions increase there has been a rise in attacks on asylum seekers.
Firecrackers were thrown at an asylum seekers’ hostel in Torgelow in the far north-east of Germany on Monday night.
And elsewhere in the east, thousands of people have marched in towns and cities in protest at asylum seekers being housed in their areas and against what they call the “Islamisation of the West”.
The head of the federal jobs agency, Frank-Juergen Weise, has called on the government to increase funding to integrate migrants more quickly into the jobs market.
Last month, EU member states agreed to take in 32,000 asylum seekers arriving in Italy and Greece over the next two years – fewer than the 40,000 target.
The UK is exempt from the agreement. Over the summer, thousands of migrants have sought to get to the UK through the Channel Tunnel from makeshift camps around Calais.