The frontline in Ukraine is "less stable than at any time since the early days of the full-scale invasion" as Russia escalates its attacks, including with the deployment of at least 10,000 North Korean troops, UK Defence Secretary John Healey has said.

"Defence intelligence will reveal today that the frontline is now less stable than at any time since the early days of the full scale Russian invasion in February 22 and we've seen in recent weeks a very clear escalation from Putin and his forces," Healy said, speaking in front of the Defense Committee, SkyNews reports.

The minister said that there had been a "very clear escalation" from Russian President Vladimir Putin and his forces and also that Moscow is increasing attacks on civilian infrastructure and he cited media reports that Russia had deployed a new type of ballistic missile against Ukraine.

"They've stepped up attacks on the energy system in Ukraine ahead of winter. They've stepped up attacks on civilian centres, killing children. They've deployed at least 10,000 North Korean troops to the battle[field], and there are unconfirmed ... media reports today of Russia firing a new ballistic missile into Ukraine, which we know they have been preparing for months," Healey stressed.

In response to a question whether the Ukrainian military actually launched Storm Shadow cruise missiles supplied by the UK at Russia for the first time, Healy said that the UK was "stepping up" and "doubling down" on its support for Ukraine, but refused to talk about any details.