Russian president Vladimir Putin has ordered a partial mobilisation of reservists in Russia, in a measure that appeared to be an admission that Moscow’s war against Ukraine was not going according to plan after nearly seven months of fighting.

It is the first mobilisation in Russia since the Second World War and comes amid battlefield losses for the Kremlin’s forces in recent weeks.

The Russian leader, in a seven-minute televised address to the nation aired on Wednesday morning, also warned the West that he was not bluffing over using all the means at his disposal to protect Russia’s territory, in what appeared to be a veiled reference to his country’s nuclear capability.

Mr Putin has previously warned the West not to back Russia against the wall and has rebuked Nato countries for supplying weapons to help Ukraine.

The total number of reservists to be called up could reach 300,000, officials said.

Even a partial mobilisation is likely to increase dismay, or sow doubt, among Russians about the war in Ukraine. Shortly after Mr Putin’s address, Russian media reported a sharp spike in demand for plane tickets abroad amid an apparent scramble to leave despite exorbitant prices for flights.

Kremlin spokesman Dmitry Peskov, who was asked what had changed since he and others previously said no mobilisation was planned, argued that Russia was effectively fighting against a combined potential of Nato because the alliance’s members had been supplying weapons to Kyiv.

Only those with relevant combat and service experience would be mobilised, Russian defence minister Sergei Shoigu said.

He added that there were around 25 million people who fitted this criteria, but only around 1% of them would be mobilised.

Another clause in the decree prevents most professional soldiers from terminating their contracts and leaving service until the partial mobilisation is no longer in place.

Mr Putin’s announcement came against the backdrop of the UN General Assembly in New York, where Moscow’s invasion of Ukraine on February 24 has been the target of broad international criticism that has kept up intense diplomatic pressure on Moscow.

Ukrainian president Volodymyr Zelensky is due to address the gathering in a pre-recorded address on Wednesday.

Mr Putin did not travel to New York.

The Russian leader’s gambit has a strong element of risk — it could backfire, by making the Ukraine war unpopular at home and hurting his own standing, and it exposes Russia’s underlying military shortcomings.

A Ukraine counteroffensive launched this month has snatched the military initiative away from Russia, as well as capturing large areas the Russians once held.

The swiftness of the counteroffensive saw Russian forces abandon armoured vehicles and other weapons as they beat hasty retreats.

A spokesman for Mr Zelensky called the mobilisation a “big tragedy” for the Russian people.

In a statement to The Associated Press, Sergii Nikiforov said conscripts sent to the front line in Ukraine would face a similar fate as ill-prepared Russian forces who were repelled in an attack on Kyiv in the first days of the invasion last February.

“This is a recognition of the incapacity of the Russian professional army, which has failed in all its tasks,” Mr Nikiforov said.

The mobilisation was unlikely to bring any consequences on the battlefield for months because of a lack of training facilities andequipment.

The US ambassador to Ukraine, Bridget Brink, tweeted that the mobilisation was a sign “of weakness, of Russian failure”.

Russian political analyst Dmitry Oreshkin said Mr Putin’s announcement smacked of “an act of desperation”. He predicted that Russians would resist the mobilisation through “passive sabotage”.

“People will evade this mobilisation in every possible way, bribe their way out of this mobilisation, leave the country,” Mr Oreshkin told the AP.

The announcement would not go down well with the general public, Mr Oreshkin said, describing it as “a huge personal blow to Russian citizens, who until recently (took part in the hostilities) with pleasure, sitting on their couches, (watching) TV. And now the war has come into their home”.

The head of the Duma defence committee, Andrei Kartapolov, said there would be no additional restrictions on reservists leaving Russia based on this mobilisation, according to Russian media reports.

The partial mobilisation order came a day after Russian-controlled regions in eastern and southern Ukraine announced plans to hold votes on becoming integral parts of Russia — a move that could set the stage for Moscow to escalate the war following Ukrainian successes.

The referendums, which have been expected to take place since the first months of the war, will start on Friday in the Luhansk, Kherson and partly Russian-controlled Zaporizhzhia and Donetsk regions.

The ballots are all but certain to go Moscow’s way.

In his address, Mr Putin accused the West of engaging in “nuclear blackmail” and noted “statements of some high-ranking representatives of the leading Nato states about the possibility of using nuclear weapons of mass destruction against Russia”.

“To those who allow themselves such statements regarding Russia, I want to remind you that our country also has various means of destruction, and for separate components and more modern than those of Nato countries and when the territorial integrity of our country is threatened, to protect Russia and our people, we will certainly use all the means at our disposal,” Mr Putin said.

He added: “It’s not a bluff.”

Foreign leaders have described the ballots as illegitimate and nonbinding. Mr Zelensky said they were a “sham” and “noise” to distract public attention.

Mr Putin said he had already signed the decree for partial mobilisation, which was due to start on Wednesday.