In order to curb the influx of immigrants, Poland will implement inspections on cars crossing the border from Slovakia, the prime minister announced on Monday.

The ruling nationalist Law and Justice (PiS) party has made migration a prominent issue in its campaign for a third term in government in an Oct. 15 election, and it has included questions about the subject in a referendum that will run concurrently with the voting.

Meanwhile, Slovakia has been dealing with an influx of illegal migrants. According to the country’s interior ministry, the number of unlawful migrants imprisoned in Slovakia has surged ninefold from a year ago to more than 27,000 so far this year.

“I instructed the interior minister to introduce controls there … on minibuses, vans, cars, buses where there is a suspicion that there are illegal immigrants there,” Mateusz Morawiecki told an election rally.

A spokesperson for the Slovak foreign ministry did not immediately respond to an emailed request for comment.

Morawiecki was speaking shortly after government spokesperson Piotr Muller said Warsaw was considering tightening controls on the border but that no decision had been taken as it wanted to consult with its partners.

“We do not want to surprise them with this decision, but we do not make this decision dependent on the consent of another country,” Muller said.

Morawiecki also hit back at German Chancellor Olaf Scholz, who on Saturday called on the Polish government to clarify allegations about a cash-for-visas scheme for migrants that has roiled Polish politics.

Morawiecki said that Scholz’s words could be a preparation for closing the border with Poland.

“You’d be better informing yourself about the actual situation and not interfering in Polish affairs,” he said, adressing Scholz.

Muller had said that the government does not rule out also strengthening controls on the border with Germany.