Poland has fortified its border with the Russian enclave of Kaliningrad, as the country’s Defense Minister Mariusz Blazak said, as tomorrow marks one year since the Russian invasion of Ukraine.

The Minister of Defense published on Twitter related photos showing that anti-tank barriers made of steel and concrete have been erected on the border, as a “preventive expansion of security measures” on the border with Russian territory, as he wrote.

Kaliningrad borders only Poland and Lithuania, members of the EU and NATO.

Last November, the Polish military began erecting a temporary 2.5-meter-high wire fence along its 232-kilometer (144-mile) border with Kaliningrad amid concerns of a new wave of migration after Moscow began allowing direct flights in the Russian enclave from Turkey and the Middle East.

Last year Poland erected a 5.5m steel fence along part of its border with Belarus after a huge increase in migrant crossings from the Middle East, Africa and Asia.