Poland, which lies on both NATO and the EU's eastern flank, has in recent years invested heavily to modernise its military following fears of a Russian threat.

"This is a historic moment ... we are truly at an absolute turning point in the effective, high-performance defence of Poland's, Europe's, and NATO's eastern border," Tusk said.

He added that Poland's borders will be "the best protected in Europe".

The cost "will be close" to 3.6 billion euros reported by Polish media earlier, Defence Minister Wladyslaw Kosiniak-Kamysz confirmed.

The system, named "San", will include 18 anti-drone batteries, 52 firing platoons, 18 command platoons and around 700 vehicles and will be fully operational in two years, he added.

The contracts signed cover Polish public and private companies as well as Norway's Kongsberg.

In a statement released Friday, the Scandinavian group said it will supply the Polish army with 18 CUAS batteries worth approximately 1.4 billion euros.

Creating an anti-drone system became an urgent necessity for Poland after Warsaw and its NATO allies had to scramble fighter jets in September when about 20 Russian drones violated Polish airspace.

San will complement a multi-layer air defence system being developed in Poland, which includes the "Wisla" programme with US medium-range Patriot systems, the "Narew" involving British short-range surface-to-air missiles and the so-called very short-range Pilica and Pilica+ programs.

The total cost of the entire air defence shield is estimated at over $ 60 billion, the defence minister said Friday.

bo/ks/ach

Kongsberg Gruppen