Russia on Wednesday said its forces had practised simulated nuclear-capable missile strikes in the western enclave of Kaliningrad, amid Moscow's military campaign in Ukraine.

The announcement came on the 70th day of Moscow's military action in the pro-Western country, with thousands killed and more than 13 million displaced in the worst refugee crisis in Europe since World War II.

After sending troops to Ukraine in late February, Russian President Vladimir Putin has made thinly veiled threats hinting at a willingness to deploy Russia's tactical nuclear weapons.

During Wednesday's war games in the enclave on the Baltic Sea located between EU members Poland and Lithuania, Russia practised simulated "electronic launches" of nuclear-capable Iskander mobile ballistic missile systems, the defence ministry said in a statement.

The Russian forces practised single and multiple strikes at targets imitating launchers of missile systems, airfields, protected infrastructure, military equipment and command posts of a mock enemy, the statement said. 

After performing the "electronic" launches, the military personnel carried out a manoeuvre to change their position in order to avoid "a possible retaliatory strike," the defence ministry added.

The combat units also practised "actions in conditions of radiation and chemical contamination".

The drills involved more than 100 servicemen.

Russia placed nuclear forces on high alert shortly after Putin sent troops to Ukraine on February 24.

The Kremlin chief has warned of a "lightning fast" retaliation if the West directly intervenes in the Ukraine conflict.

Observers say that in recent days, Russia's state television has attempted to make nuclear weapons use more palatable to the public.

"For two weeks now, we have been hearing from our television screens that nuclear silos should be opened," Russian newspaper editor and Nobel Peace Prize laureate Dmitry Muratov said on Tuesday.