He cited the need to curb uncontrolled migration flows and respond to what he described as asymmetrical actions by neighbouring states.
Speaking at a press conference ahead of a Cabinet meeting, Tusk said the decision had been made earlier that day and that the Border Guard and other services would spend the coming days preparing the operation.
The formal regulation is being drafted by the Ministry of the Interior and Administration.
Tusk said that the move was prompted by Germany's ongoing refusal to accept back migrants trying to reach its territory, a departure from past practice.
"This has led to tensions and a justified sense of asymmetry," the prime minister said.
"Without checks on our side, it’s difficult to verify whether the people being sent back to Poland should be returned at all," he added.
Germany introduced its own border checks with Poland in October 2023 in an effort to prevent illegal migration. These were initially meant to last until September this year.
On Tuesday, Tusk said that Berlin had decided to extend the checks, "somewhat against the spirit of the Schengen Borders Code and European law."
"Our response will be symmetrical," he added. "The time when Poland failed to respond adequately to this type of action is over."
Tusk insisted that Poland remains committed to the principle of borderless travel within the European Union.
"We were defenders of Schengen and still are," he said, "but this must be a shared, symmetrical will among neighbours."
In the case of the border with Lithuania, Tusk said the reintroduced checks would apply not only to official crossings but also to so-called "green border" areas such as forests and local roads.
These operations will be supported by Poland's Territorial Defence Force (WOT) and other military units.
Anyone found crossing the Polish-Lithuanian border illegally will be returned to Lithuania, he said, "in accordance with the rules and regulations."
The prime minister acknowledged that the measures would also affect Latvia and Estonia to some extent.
He called on all three Baltic states, as well as the broader European Union, to work more closely with Poland to disrupt what he described as large-scale people-smuggling operations orchestrated by Russia and Belarus.
"If Europe shows greater firmness on sanctions, including action against airlines involved in these operations, and especially against Belarus, we won’t need to close any Schengen borders," Tusk said.
"But if this continues, [Belarusian leader Alexander] Lukashenko and his services will soon see that we’re ready for very unpleasant and tough steps," he added.
Tusk also condemned "the politicisation of the migration issue."
In recent days, opposition MPs have accused German authorities of unlawfully transporting migrants into Poland and have shared such claims online.
Right-wing activists have begun organising so-called "citizens’ patrols" on the German border, attempting to inspect vehicles and posting videos of their actions.
Tusk called such behaviour "shameful and scandalous."
"Anyone who politically supports these kinds of activists—who disrupt the work of the Border Guard and even attack its officers—is undermining the state’s ability to ensure public safety," he said.
Since April, Poland’s Border Guard has been conducting Operation Bridge along the German border, supported by the national police.
So far, they have checked 4,500 foreign nationals and detained 250 for unlawful residence. A total of 2,000 people have been detained this year, including suspected smugglers.
Opposition politicians, including Law and Justice (PiS) party leaders Jarosław Kaczyński, have accused the government of being too passive.
(rt/gs)
Source: IAR, PAP
Click on the audio player above for a report by Agnieszka Bielawska.