Interior Minister Nancy Faeser said asylum claims were on the rise with many people arriving via the Balkans or the Mediterranean.
It came as an annual police report showed illegal entries to Germany climbing to their highest level in four years.
Those figures only covered 2021, but Ms Faeser said the upward trend had continued this year.
It is separate from the refugee crisis in Ukraine, where people fleeing the war normally have permission to stay in the EU.
“As well as the many refugees from Ukraine, the number of people coming to Europe via the Mediterranean and the Balkans is noticeably rising again,” Ms Faeser told a press conference.
“The number of asylum applications has risen in the past few months, as well as the number of illegal entries.”
Checks on the Austrian border will be extended until May, while more random inspections are taking place on the Czech border, Ms Faeser said.
Germany has also succeeded in persuading Austria and the Czech Republic to order checks on their borders with Slovakia.
Austrian checks on Slovakia will be in place for at least a month, and on Slovenia and Hungary until at least May.
Countries in the EU’s visa-free Schengen zone are allowed to bring in temporary checks to head off what they see as security threats.
“We want to protect people fleeing to us from war and political persecution. We stand by our humanitarian responsibilities,” Ms Faeser said.
“But nobody should put their lives in danger on the dangerous migration routes if they have no perspective in Europe.”
The report by Germany’s federal police said 57,637 illegal entries were recorded last year, a rise of 63 per cent and the highest level since 2017.
About half of them entered from Poland or Austria, but all nine of Germany’s land borders saw some activity.
Numbers were swelled by the crisis in Belarus, where the government allegedly ferried migrants to the border to stoke chaos in the EU.
That led to increased pressure on the German-Polish border as migrants tried to reach Germany in lorries or on foot.
Two people were reported to have died while being smuggled to Germany from Belarus.
Other asylum seekers had already been granted protection in Greece but were trying their luck again in Germany, the report said.
EU border agency Frontex said last month that illegal entries to the bloc were at their highest by that stage of the year since 2016.
More than 100,000 people have entered this year from countries in the western Balkans, primarily from Syria, Afghanistan or Turkey, it said.
Italy is meanwhile taking a harder line on crossings in the Central Mediterranean, which especially involves Tunisian, Egyptian and Bangladeshi migrants.
Prime Minister Giorgia Meloni this week infuriated France by turning away a ship with 230 migrants on board, which docked at a French port on Friday.
France retaliated by withdrawing an offer to take in 3,500 migrants to ease the burden on Italy.