Germany has recorded 5,700 illegal entries it says are linked to Belarus.
Hundreds of police officers are guarding the German-Poland border because of an influx of migrants arriving from Belarus, according to Germany's interior minister.
Horst Seehofer said that "hundreds of officers are on duty day and night" and that "if necessary, I am ready to reinforce them even further".
"I am convinced, in the spirit of the European idea, that we must know who is coming to us. It is legitimate that we protect the external border in such a way that undetected border crossings are prevented," he added in an interview published in Bild am Sonntag.
The announcement came as German police were called in on Sunday morning to disperse about 50 supporters of the far-right "Third Way" militia that intended to patrol the border area itself to turn back foreigners seeking to enter.
This movement is considered violent and dangerous by the Internal Intelligence Service. Officers seized a machete, a bayonet, sticks and pepper spray.
Poland and Baltic countries Latvia and Lithuania have declared states of emergency at their border with Belarus because of an influx of migrants. The European Union has accused Minsk of facilitating migration into the bloc to retaliate against sanctions Brussels imposed on Belarusian officials and entities over the disputed August 2020 presidential election.
The EU's border agency, Frontex, said earlier this month that Lithuania is the most impacted with 4,170 illegal border crossings detected since the beginning of the year, while Poland saw 1,380 during that same time period. Figures for Latvia were not provided.
The German Interior Ministry said last week that it had registered 5,700 illegal entries into Germany linked to Belarus.
The EU has warned airlines -- that ferry would-be asylum seekers to Belarus -- that they could be hit with sanctions as well. An Iraqi airline has "promised to suspend flights to Belarus", according to the German Interior Ministry.
But the three EU member states neighbouring Belarus — as well as Austria, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Greece, Hungary, and Slovakia — have asked Brussels to go even further, including funding the construction of a barbed-wire fence, which Commission President Ursula von der Leyen rejected at a summit on Friday.
Lithuania has started building the fence while Poland has asked the EU to provide €350 million.
Seehofer, who has ruled out closing the border with Poland, wrote to his Polish counterpart Mariusz Kaminski last week to propose increasing joint patrols along the border in the face of growing numbers of migrants.
Mariusz Kaminski replied that Poland would give its "full support" to such measures.
At least eight people have died at the border area since the end of summer with authorities in Belarus and Poland accused of carrying out illegal push-backs.