Poland will spend over 2.3 billion euros ($2.5 billion) to fortify its eastern border, the EU's eastern flank, against potential enemies, Prime Minister Donald Tusk said on Saturday.

"We have taken the decision to invest 10 billion zlotys for our security and above all to secure our eastern border," he said, calling the project an "eastern shield".

Poland's eastern border includes Belarus, Ukraine and the Russian exclave of Kaliningrad.

"The reinforcement of 400 kilometres (about 250 miles) of border with Russia and Belarus will be an element of dissuasion, a strategy to push back the war at our frontiers," he said, adding that the work had not started.

Since the start of the Russian invasion of Ukraine in February 2022, Warsaw has staunchly backed Kyiv and been a transit route for arms being supplied by Ukraine's Western allies.

Warsaw has also modernised its army and raised defence spending to four percent of GDP, one of the highest in the European Union.

It has also acquired billions of dollars of military equipment, mainly from the United States and South Korea.