Moscow/IBNS: Acting on President Vladimir Putin's orders, Russia's nuclear forces on Tuesday began a special drill exercise amid its ongoing war with Ukraine, media reports said.

The action comes at a critical point in the Ukraine war which senior Russian officials termed as the "most difficult phase", as quoted by Reuters.

This is the second such military exercise initiated by Putin in 15 days.

Meanwhile, the West-led NATO alliance is still unsure of how to deal with the escalating situation.

The escalation was a result of Western forces, led by the US, planning to allow Ukraine the use of long-range cruise missiles to target territories deep inside Russia.

Moscow earlier said that if Ukraine would undertake such a move with the backing of the West, it would also consider the use of its nuclear power as a defensive action.

The Kremlin had said that its updated nuclear doctrine, which was approved by Putin last month, allows Moscow to use nuclear power against non-nuclear states and that it should be seen as a warning to the West.

"We will work out the actions of officials to control the use of nuclear weapons with practical launches of ballistic and cruise missiles," President Putin said in a clip from the launch as quoted by Reuters.

"Using nuclear weapons would be an extremely exceptional measure but they need to be kept ready for use."

Putin also mentioned that: "We are not going to get involved in a new arms race, but we will maintain nuclear forces at the level of necessary sufficiency."