Russian President Vladimir Putin has signed treaties for an illegal annexation of occupied Ukrainian territory in a sharp escalation of his seven-month invasion of Ukraine.

He vowed to protect the newly annexed regions by “all available means”, a nuclear-backed threat at a Kremlin signing ceremony where he also railed at the West.

Ukraine’s leader immediately countered with a signing ceremony of his own, releasing video of him putting pen to papers that he said were a formal Nato membership request.

Mr Putin’s land-grab and President Volodymyr Zelensky’s signing of what he said is an “accelerated” Nato membership application sent the two leaders speeding even faster on a collision course that is cranking up fears of a full-blown conflict between Russia and the West.

The Russian leader has repeatedly made clear that any prospect of Ukraine joining the world’s largest military alliance is one of his red lines and it was among the justifications he has cited for his invasion.

In his speech, Mr Putin urged Ukraine to sit down for peace talks but immediately insisted he would not discuss handing back occupied regions — keeping him at odds with the Ukrainian government and its western backers which have rejected his land-grab.

Mr Zelensky said there would be no negotiations with Mr Putin, adding: “We are ready for a dialogue with Russia, but… with another president of Russia.”

In a Kremlin ceremony at the ornate St George’s Hall to herald the annexation of the occupied parts of Ukraine, Mr Putin accused the West of fuelling the hostilities as part of what he said is a plan to turn Russia into a “colony” and a “crowd of slaves”.

The hardening of his position, in a conflict that that has killed and wounded tens of thousands of people, further cranked up tensions, already at levels unseen since the Cold War.

The European Union responded to Mr Putin’s latest step with a joint statement rejecting and condemning “the illegal annexation” of the four regions: Donetsk, Luhansk, Kherson and Zaporizhzhia.

The EU’s 27 member states said they will never recognise the illegal referendums that Russia organised “as a pretext for this further violation of Ukraine’s independence, sovereignty and territorial integrity”.

Ukraine vowed to continue fighting, and Mr Zelensky announced the “accelerated” Nato application, although it was not immediately clear what that would mean, since it requires the unanimous support of the alliance’s members.

“De facto, we have already proven compatibility with alliance standards. They are real for Ukraine – real on the battlefield and in all aspects of our interaction,” Mr Zelensky said.

“We trust each other, we help each other, and we protect each other. This is the alliance.”

The Kremlin ceremony came three days after the completion in occupied regions of Moscow-orchestrated “referendums” on joining Russia that were dismissed by Kyiv and the West as a bare-faced land grab held at gunpoint and based on lies.

But Mr Putin, in a fiery speech at the ceremony, insisted that Ukraine must treat the Kremlin-managed votes “with respect”.

After the signing ceremony of treaties to join Russia, Moscow-installed leaders of the occupied regions gathered around Mr Putin and linked hands, before joining chants of “Russia! Russia!” with the audience.

Mr Putin also railed at the West, cutting an angry figure as he accused the US and its allies of seeking to destroy Russia. He said the West acted “as a parasite” and used its financial and technological strength “to rob the entire world”.

He portrayed Russia as being on a historical mission to reclaim its post-Soviet great power status and counter western domination which he said is collapsing.

“History has called us to a battlefield to fight for our people, for the grand historic Russia, for future generations,” he said.

Russia later vetoed a UN Security Council resolution would have condemned the referendums, declared that they have no validity and urged all countries not to recognise the annexation.

China, India, Brazil and Gabon abstained on the vote in the 15-member council.

The separatist Donetsk and Luhansk regions in eastern Ukraine have been backed by Moscow since declaring independence in 2014, weeks after the annexation of Ukraine’s Crimean peninsula.

The southern Kherson region and part of neighbouring Zaporizhzhia were captured by Russia soon after Mr Putin sent troops into Ukraine on February 24.

Both houses of the Kremlin-controlled Russian parliament will meet next week to rubberstamp the treaties for the regions to join Russia, sending them to Mr Putin for his approval.

He has bluntly warned Ukraine against pressing an offensive to reclaim the regions, saying Russia would view it as an act of aggression – threats that Moscow can back up with the world’s largest arsenal of nuclear warheads.

Russia controls most of the Luhansk and Kherson regions, about 60% of Donetsk and a large chunk of Zaporizhzhia, where it took control of Europe’s largest nuclear power plant.

Mr Zelensky vowed to keep fighting, saying: “The entire territory of our country will be liberated from this enemy. Russia already knows this. It feels our power.”