"I instructed the interior minister to introduce controls there... on minibuses, vans, cars, buses where there is suspicion that there are illegal immigrants," he said.
Morawiecki, who made the remarks at a campaign event, said the move was designed to halt traffic on a new, unauthorized migrant route to Germany.
"We don't want anyone alleging that our border is porous," said Morawiecki.
Warsaw dealing with unpleasant migration scandal during election campaign
The announcement comes on the heels of German Chancellor Olaf Scholz calling for Polish clarification on reports that Warsaw's embassies in Africa and Asia were selling temporary EU work visas for thousands of dollars each.
A top diplomat has been fired and the Polish embassy in Nairobi, Kenya, is under investigation as a result of the scandal. Yet, despite the belief that the scheme was run from within his department, Foreign Minister Zbigniew Rau has refused to step down.
Scholz, who has faced criticism at home for not doing enough to curb migrant arrivals, told the German news agency DPA this weekend that Warsaw would have to be transparent, "I don't want people to just be waved through from Poland and us to have a discussion about asylum policy afterward."
Polish Foreign Minister Rau called on Scholz, "to respect Poland's sovereignty and refrain from statements that damage our mutual relations."
Rau has now accused Scholz of meddling in Poland's internal affairs just weeks before the ruling ultra-conservative Law and Justice (PiS) party hopes to win a third term in power in elections set for October 15 — PiS has made illegal migration a central issue in its nationalist campaign.
Scholz spokesman Steffen Hebestreit on Monday said, "I can't see any interference in any election campaign," adding that it was "perfectly normal" for the chancellor to be commenting on a situation "in which Germany is massively affected."
Schengen suspended as countries struggle to control border amid migrant influx
Last week, German Interior Minister Nancy Faeser acknowledged Berlin was in talks with Poland and the Czech Republic about introducing temporary border checks to stop the influx of migrants into Germany.
At the time, Faeser said the border presence would come in addition to random police checks already being carried out.
In practice, several states carry out some form of checks at certain borders within Schengen.
Still, many countries have struggled to control the large number of people coming to the EU from Asia, the Middle East and Africa. Slovakia in particular has seen a large increase in arrivals. Authorities there say they have detained more than 27,000 people so far this year — nine times more than during the same period last year.
js/ab (AP, Reuters)