Russia launched major military exercises Thursday, with thousands of troops taking part in war games across the country, including in the annexed Crimean peninsula and southern regions near Ukraine.

More than 8,000 ground troops began drills set to last until early April in regions including southern Russia, Crimea, Armenia and the breakaway Georgian regions of South Ossetia and Abkhazia, defence ministry officials said.

The exercises are among the largest in recent times, the RIA Novosti news agency reported.

Russia’s Black Sea fleet based in Crimea also began separate drills, using military planes to simulate an attack on its missile-carrying ships.

The navy also held exercises in the far eastern Sea of Japan and the far northern Barents Sea.

Around 200 Russian troops in central Russia underwent training to simulate urban warfare, using tanks and armed personnel carriers to “storm a city,” defence officials said.

In February, Russia launched massive drills involving several thousand soldiers close to its borders with Baltic states already jittery over their former Soviet master’s actions in Ukraine.

The United States then launched a three-month military exercise in Estonia, Latvia and Lithuania, deploying some 3,000 frontline troops to take part in drills in what officials said was meant to “demonstrate resolve to President (Vladimir) Putin and Russia that collectively we can come together.”

Putin last year ordered a series of snap drills in regions bordering Ukraine, and Moscow massed up to 40,000 troops along Ukraine’s eastern border, according to NATO.

He has since been accused by the West of backing and arming separatist rebels in eastern Ukraine in a conflict that has left some 6,000 dead. The Kremlin denies this.

NATO is countering Russia by boosting its defenses on Europe’s eastern flank with a spearhead force of 5,000 troops and command centres in the Baltic states, Bulgaria, Poland and Romania.