Belarus said on Monday its army was taking part in the second stage of Russian exercises ordered by President Vladimir Putin to practise the deployment of tactical nuclear weapons.

The first phase of the drills took place in southern Russia last month, in what nuclear analysts said was a warning signal by Putin to deter the West from wading more deeply into the war in Ukraine.

Belarusian Defence Minister Lieutenant General Viktor Khrenin said the exercises were a proactive measure to "increase our readiness to use so-called retaliatory weapons".

"Now, more than ever before, we are determined to respond to any threats posed to both our country and the Union State" between Russia and Belarus, he said.

He did not say where the exercises were taking place or what types of weapons were involved. Belarus shares borders with three NATO countries - Poland, Lithuania and Latvia.

"We have no goal of creating any tension in regional security issues. We do not project relevant military threats on third countries or anyone else," Khrenin added.

"We are a peaceful state, we do not threaten or seek confrontation with anyone, but we will keep our powder dry!"

Putin and Belarusian leader Alexander Lukashenko announced last year that Russia was moving some of its tactical nuclear weapons to Belarus. These are warheads designed for use on the battlefield, as opposed to long-range strategic weapons intended to wipe out entire enemy cities.

Some Western analysts believe tactical nuclear weapons have acquired greater importance in Moscow's thinking since the start of the war in Ukraine, where its conventional forces struggled in the first two years.

In theory the use of such a weapon could deliver a stunning shock to the West without necessarily prompting a full-blown nuclear war, though the risk of triggering a cycle of escalation would be huge. Since day one of the war, Putin has repeatedly warned the West about the size and power of Russia's nuclear arsenal.

There was no immediate information from Russia about the exercises with Belarus, although Moscow had announced earlier that they would take place.

The first phase last month took place in the Akhtubinsk region of southern Russia, according to geolocation confirmed by Reuters, and involved Iskander and Kinzhal missiles.

Russia's foreign ministry said last month it hoped the exercises would "cool the hot heads in Western capitals" after French President Emmanuel Macron floated the possibility of sending European troops to fight Moscow in Ukraine, and British Foreign Secretary David Cameron said Kyiv had the right to use weapons provided by London to strike targets inside Russia.