Britain has warned Vladimir Putin "it would be war" if a "single toecap" of Russian troops enters any NATO territory.
The statement from Sajid Javid comes as Russian forces targeted a villiage just a few miles from the Polish Border.
A military base in Yavoriv was bombed in a deadly barrage of missiles on Sunday, as 35 people were killed and 134 were injured.
Locals claimed that the “skies turned red” when they were wakened during the night with sirens as the war in Ukraine intensifies.
The Health Secretary blasted the attack and reiterated NATO's stance that if Putin moves onto their territory he faces a war with 30 countries.
"If just a single toecap of a Russian soldier steps into NATO territory then it would be war with NATO," he told Sky News.
In another interview he said "it's not impossible" that Russia would launch an attack on Nato territory but he thinks it is "very unlikely".
The UK and other NATO countries have so far resisted sending troops into Ukraine amid fears it could cause a dramatic escalation in the conflict with nuclear-armed Russia.
It comes after a Russian opposition politician said Vladimir Putin will "destroy the world" if left unchecked and global leaders should brace for the Kremlin to deploy nuclear weapons, report Mirror Online.
Leonid Volkov, the former chief of staff for jailed Putin critic Alexei Navalny, issued the grim warning on Sunday - and said he wanted his fellow Russians to make it clear it was "not our war".
Mr Javid also accused Russia of committing a war crime by attacking a maternity hospital in Mariupol, with the WHO declaring that 31 atrocities have been committed at health facilities.
It emerged on Monday that a mother and baby who were pulled from the rubble have now died.
The image of the stricken mum being stretchered away from the destruction sent shockwaves around the world.
Javid said: "In fact, the most recent information I have from the World Health Organisation is they now have documented evidence of at least 31 such attacks of health facilities hospitals, including shelling.
"A couple of days ago of a cancer hospital, as well. So these are war crimes."
Justice Secretary Dominic Raab will travel to The Hague today to offer Britain's help to gather the evidence of potential war crimes committed in Ukraine.
Boris Johnson will also host Nordic and Baltic leaders this week to discuss security as the Russian onslaught continues.
In a call with Ukrainian president Volodymyr Zelensky on Sunday, the Prime Minister said the UK would "continue to pursue more options for bolstering Ukraine's self-defence".
No 10 said Johnson told Zelensky that Russian president Vladimir Putin's "barbaric actions" were "testing not just Ukraine but all of humanity".
It comes as a new scheme to allow Brits to take Ukrainian refugees into their homes was due to be launched today.
Levelling Up Secretary Michael Gove is expected to set out more details in the Commons, before a website goes live allowing people to register their interest.
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