Germany could receive up to 1.5 million asylum-seekers this year, according to a newspaper quoting a confidential document containing estimates that are far higher than publicly released official figures.
Authorities have so far predicted that Europe's biggest economy would record between 800,000 and one million new arrivals in 2015.
But Bild paper quoted the document saying that the authorities were now expecting to receive 920,000 new arrivals in the coming three months alone, bringing the total number of asylum-seekers this year to 1.5 million.
"The migratory pressure will increase. For the fourth quarter, we expect between 7,000 and 10,000 illegal entries a day," according to extracts of the document, although Bild did not specify its source.
The document said: "The significant number of asylum-seekers risks becoming an extreme burdenfor the regions and communes."
The newspaper also quoted the document estimating that each asylum-seeker who successfully obtained refugee status could bring on average "four to eight" family members to Germany.
On the basis of the preliminary forecast of 920,000 refugees, some "7.36 million people" could therefore have the right to move to Germany due to family ties.
Chancellor Angela Merkel has been lauded worldwide for her decision to open Germany's doors to refugees fleeing war and misery.
But within Germany, her popularity is starting to wane as local authorities struggle to cope with the massive task of hosting the record surge in refugees.
Many of those who come to Germany and other EU state arrive after arduous trips that can involve being on overcrowded boats in the Mediterranean.
Children bodies found
Nearly 3,000 others have died or disappeared during the crossing.
On Sunday, decomposed bodies belonging to a baby, estimated to be 6-12 months old, and a child, about four years old, were found on the shore of the Greek Kos island, on the frontline of the refugee influx coming from Turkey.
According to Greek media reports, authorities believe the children belonged to refugee families trying to reach Kos in a dinghy.
The grim discovery recalls the case of three-year-old Syrian boy Aylan Kurdi whose body was found face down on a Turkish beach last month.
Read more: Europe's policy did not kill Aylan Kurdi
In September, at least 15 babies and children drowned when their overcrowded boat capsized in high winds off the Aegean island of Farmakonisi.
According to a Frankfurter Allgemeine Sonntagszeitung report on Sunday, the EU and Turkey have agreed in principle to a plan of action to help ease the flow of refugees into the bloc.
Under the plan, Turkey would agree to stepped-up efforts to secure its frontier with the EU by taking part in joint patrols with the Greek coastguard in the eastern Aegean Sea coordinated by EU border protection agency Frontex.