Germany on Wednesday ordered new border checks for people arriving from Poland and the Czech Republic, taking on what it calls a worsening human trafficking problem.
Guards have been instructed to set up mobile checkpoints and vary their location to keep the smugglers on their toes.
Borders are usually open between the three Schengen zone countries but authorities are under pressure to stem the flow of migrants.
Illegal crossings have been reported almost daily, with four alleged traffickers from Syria, Belarus and Georgia arrested early on Wednesday near the Polish border. Germany recorded a 77 per rise in first-time asylum requests in the first eight months of the year, according to official data.
German Interior Minister Nancy Faeser – a candidate in upcoming regional elections at which migration is a key talking point – called for "maximum pressure" on the smugglers.
She said the new measures were meant to protect "people who are often smuggled across borders with no water and barely any oxygen".
"We have to stop the cruel trade of the smugglers who put human lives on the line to maximise profit," Ms Faeser said.
The moving border posts are meant to stop traffickers making "evasive movements" but officials will try to keep disruption to local commuters to a minimum, she said.
The announcement comes on the eve of talks among the EU's 27 members to agree on a way forward on migration. There are fears in Germany that a hard-fought compromise to manage asylum claims at European level could be undermined by new emergency measures.
Under a plan agreed to in principle in June, EU countries would be asked to show "compulsory solidarity" with frontline states such as Italy, in exchange for stricter laws to limit the number of asylum seekers arriving in the bloc in the first place.
Ms Faeser said inspection-free travel within Europe was "in danger" if the bloc could not tighten its external borders.
Concerns over migration have been blamed in part for a polling surge for the far-right Alternative for Germany (AfD) party. Two states go to the polls on October 8, with Ms Faeser leading the Social Democratic Party into the contest in Hesse.
Towns and cities have complained they are overstretched due to migration pressure, evoking memories of 2015 when Germany took in hundreds of thousands of Syrian refugees.
Ahead of the election in his state, Bavaria's conservative premier Markus Soeder suggested an upper limit on asylum seekers of 200,000 annually – a proposal rejected by Ms Faeser.
There have previously been random police checks at the borders. Germany has also reintroduced border posts on its southern frontier with Austria.
