Thousands of Polish and other NATO troops have launched major defensive exercises in Poland’s north amid security concerns raised by war games recently held by neighboring Russia and Belarus, The Washington Post reported Friday.

The Dragon-17 exercise involves some 17,000 land, air force and navy troops and some 3,500 units of equipment and runs through September 29.

For the first time the biannual drill is being joined by Poland’s new Territorial Defense Forces, which train civilian volunteers to support regular troops. Cybersecurity is also being tested.

On Thursday, Deputy Defense Minister Michal Dworczyk visited the Drawsko Pomorskie test range in northwest Poland, the main site of land drills for Poland’s biggest military exercise this year.

He said the drills were of defensive nature and contrasted them with the just-ended Zapad (West) 2017 maneuvers. Dworczyk said the joint Russian-Belarusian war games had a "very clear offensive trait."

He earlier said the NATO drills now underway test defensive operation between Polish troops and those deployed in Poland by NATO and by the US in response to the region’s concerns over Russia’s military activity.