He also made fresh nuclear threats against the West, claiming Western nations had engaged in “nuclear blackmail” against Russia and “gone beyond all limits in its aggression”, warning he has “lots of weapons to reply”.
The escalation comes after a difficult period for Russia, which has seen the Ukrainian military push back Russian forces.
Russia has been forced to withdraw from large swathes of land in the north-eastern Kharkiv region following Ukrainian counter-attacks in recent weeks, and there have been suggestions its forces have been suffering from shortages.
Here’s what Mr Putin’s recent actions could mean for the UK, and how the Government has responded.
Could the UK go to war with Russia?
The UK’s stance on going to war with Russia has not changed.
The only thing that would trigger such an event is if Russia was to move beyond Ukraine and attack a Nato country.
Nato uses a system of collective security, whereby its independent member states agree to mutual defence in response to an attack by any external party.
That means if Russia were to invade, say Poland, Lithuania, Latvia or Estonia, it would automatically be at war with all 30 Nato members, including the UK and US. Given Russia has been forced to call up reservists, suggesting its military has been depleted, any further invasion appears very unlikely at this stage.
It is also very unlikely Russia makes a direct attack on the UK, despite Mr Putin’s threats, as it would amount to global escalation.
“If the territorial integrity of our country is threatened, we use all available means to protect our people – this is not a bluff,” Mr Putin said on Wednesday.
He reiterated his intent to stand up to what he believes is Western aggression, despite it being Russia that started the war in Ukraine.
“The territorial integrity of our motherland, our independence and freedom will be secured, I repeat, with all the means we have,” he said.
“Those who try to blackmail us with nuclear weapons should know that the prevailing winds can turn in their direction.”
Asked whether it was possible for a Russian nuclear missile to hit London, Sergei Markov, a former advisor to Putin, said: “Yes it is possible.”
He told BBC Radio 4’s Today programme that the situation could arise “if Great Britain continue to be aggressor against Russia, if Prime Minister of Great Britain Liz Truss still has plans to destroy Russia”.
He added: “People in London should understand that this threat comes from Liz Truss, who is the aggressor.
“Stop the war against Russia on the Ukrainian territory.”
Foreign Office minister Gillian Keegan said Mr Putin’s threats should be taken “very seriously”, and described the speech as a “worrying escalation” of global tensions over the war in Ukraine.
“Some of the language there was quite concerning at the end and obviously we would urge for calm.”
“It’s something that we should take very seriously because, you know, we’re not in control,” she told Sky News. “I’m not sure he’s in control either really. This is obviously an escalation and, of course, for the Russian people now they will be conscripted into this war.”
Defence Secretary Ben Wallace accused Putin of “breaking his own promises not to mobilise parts of his population” and said that the speech was “an admission that his invasion is failing”.
“He and his defence minister have sent tens of thousands of their own citizens to their deaths, ill equipped and badly led,” he said in a statement.
“No amount of threats and propaganda can hide the fact that Ukraine is winning this war, the international community are united and Russia is becoming a global pariah.”
The European Commission described the announcement as a “very dangerous nuclear gamble”, adding that the international community must apply pressure to Putin to “stop such behaviour”.
What does Putin’s partial mobilisation mean?
Russia’s defence minister Sergei Shoigu said that the partial mobilisation would see 300,000 reserves called up to serve in Ukraine.
He added that those who served as conscripts or students were not included.
In a televised address to the Russian people, Mr Putin said: “Today our armed forces are operating across a frontline that exceeds 1,000 km, opposing not only neo-Nazi formations but the entire military machine of the collective West.
“In such a situation, I consider it necessary to make the following decision, which is fully appropriate to threats we face.
“Namely, in order to protect our motherland, its sovereignty and territorial integrity, and to ensure the safety of our people and people in the liberated territories, I consider it necessary to support the proposal of the defence ministry and the general staff to conduct a partial mobilisation in the Russian federation.”