Ukrainian forces are re-occupying towns previously seized by Moscow as Russian army morale continues to fall, according to UK officials.
The ministry of defence (MoD) said Ukraine has “launched strikes against high value targets in Russian-occupied areas”, including a landing ship and ammunition storage depots.
This has allowed them to re-take towns near to the capital Kyiv, the MoD said.
The assessment came amid fresh warnings that Russia is preparing to use chemical weapons as it tries to inject fresh impetus into its stalling military campaign.
US president Joe Biden said such a move would “trigger a response in kind” from NATO.
In an intelligence briefing posted on Twitter last night, the MoD said Ukrainian forces “will continue to target logistical assets in Russian-held areas”.
They added: “This will reduce Russia’s ability to conduct offensive operations, and further damage already dwindling morale.”
In a further update this morning, the MoD said: “Ukrainian counter-attacks, and Russian Forces falling back on overextended supply lines, has allowed Ukraine to re-occupy towns and defensive positions up to 35 kilometres east of Kyiv.
“Ukrainian Forces are likely to continue to attempt to push Russian Forces back along the north-western axis from Kyiv towards Hostomel Airfield.”
Meanwhile, Boris Johnson has pledged that the UK will “ramp up lethal aid to Ukraine” as its forces resist Vladimir Putin’s invasion.
Speaking after an emergency NATO summit in Brussels, the prime minister said: “We will not stand by while Putin vents his fury on Ukraine.”
And speaking to the BBC’s Newsnight programme, the PM said Ukraine “can certainly win” the war.
He said: “I don’t think it’s going to be easy, I think that the situation for the Ukrainians is grim, miserable.
“I don’t think that we’ve seen anything like it for 80 years in Europe and what (Vladimir) Putin is doing is unconscionable.
“But there’s a sense in which Putin has already failed or lost because I think that he had literally no idea that the Ukrainians were going to mount the resistance that they are and he totally misunderstood what Ukraine is.
“And far from extinguishing Ukraine as a nation he is solidifying it.”