Serbia’s president has issued a stark warning regarding the ongoing Russia-Ukraine conflict, claiming that Vladimir Putin is ‘not bluffing’ about the potential use of nuclear missiles.

According to Serbian publication Novosti, President Aleksander Vucic, one of Putin’s allies who claims to know the Russian leader ‘very well’, told journalists: ‘Don’t think that someone somewhere is bluffing, unfortunately, nobody is bluffing and, unfortunately, we are walking into mild disaster’.

Vucic’s ominous comment comes after Ukraine carried out its first strike on Russian territory with a US-supplied long-range missile on Tuesday – just days after the Biden administration gave Kyiv the green light despite fears it could escalate the conflict beyond control.

Meanwhile, Polish Prime Minister Donald Tusk said on Friday that there is a real risk of a global conflict breaking out after Russia fired a hypersonic intermediate-range ballistic missile at a Ukrainian city.

Putin had said on Thursday that the strike was a response to the U.S. and UK allowing Kyiv to strike Russian territory with advanced Western weapons, a move he said had given the conflict ‘elements of a global character’.

Ukrainian President Volodymyr Zelenskiy called the Russian missile strike another escalation after deployment of North Korean troops on Russian soil.

‘The war in the east is entering a decisive phase, we feel that the unknown is approaching,’ Tusk told a teachers conference.

‘The conflict is taking on dramatic proportions. The last few dozen hours have shown that the threat is serious and real when it comes to global conflict.’

Poland, which borders Ukraine, Russia and Belarus, has been a leading voice calling for members of NATO to spend more on defence, and is itself allocating 4.7% of gross domestic product to boosting its armed forces in 2025.

Russia said on Thursday that a new U.S. ballistic missile defence base in northern Poland will lead to an increase in the overall level of nuclear danger, but Warsaw said ‘threats’ from Moscow only strengthened the argument for NATO defences.

Earlier today, Ukraine’s former military chief warned that World War Three is already underway – with Vladimir Putin’s autocratic allies, North Korea, Iran and China, openly supporting his forces on the battlefield.

Valery Zaluzhny, who is now Ukraine’s envoy to the United Kingdom, told the UP100 award ceremony in Kyiv: ‘I believe that in 2024 we can absolutely believe that the Third World War has begun.’

The General said that as of this year, ‘Ukraine is no longer facing Russia. Soldiers from North Korea are standing in front of Ukraine.’