Russia is continuing work to put its ‘unstoppable’ Satan II intercontinental ballistic missile –  part of its terrifying strategic nuclear arsenal – on combat duty, Moscow’s state media has revealed.

The Satan II missile, also referred to as the RS-28 Sarmat, is designed to deliver nuclear warheads to strike targets thousands of miles away in the United States or Europe, but its development has been dogged by delays and testing setbacks.

In September, Putin faced humiliation after his Satan II missile exploded, obliterating Russia’s only test site for hypersonic weapons.

As a result, experts said that the test programme for the rocket could be delayed for years, or could even be aborted after a series of failed launches.

But as Putin continues work on testing his Satan II missile, Moscow warned yesterday that retaliatory actions are being prepared after accusing Ukraine of launching another round of ATACMS strikes into Russian territory.

The US gave Ukraine permission to use the weapons to hit Russian territory just over a week ago, after months of requests from Kyiv.

A fiery explosion at an ammunition depot in Karachev around 75 miles from the Ukrainian border in Russia’s Bryansk region lit up the night sky last week following the ATACMS strike.

It was also believed that Ukraine may have used British-supplied Storm Shadow missiles to strike a secretive Russian presidential facility in the Kursk region.

The Kremlin had previously threatened a ‘nuclear response’ should Ukraine hit targets on Russian soil with Western-supplied long-range munitions.

Britain’s Storm Shadow missiles are capable of dodging air defences – making them a nightmare attack weapon for their enemy.

The £800,000 rockets use GPS technology to precisely blast targets, and can travel through the air at 600mph.

Storm Shadow missiles have already been used by Ukraine inside its own territory for some time, but Kyiv now appears to have been granted permission to use the weapons to strike within Russia.

It comes after the New York Times reported last week that some unidentified Western officials said that it was possible US President Joe Biden could give Ukraine nuclear weapons before the end of his presidency.

Meanwhile, the Russian foreign ministry said on Wednesday that such an idea would be ‘insane’ and that preventing that scenario was one of the reasons why Moscow went into Ukraine.

Maria Zakharova, a spokesman for the ministry, said it was in the interests of responsible governments to ensure that such a scenario, which she called ‘suicidal’, did not unfold.

She said that what she called ‘irresponsible actions’ by Ukraine and its Western backers could bring the world to ‘the brink of catastrophe.’

Additionally, Putin’s troops have been advancing westward in Ukraine at a rate faster than any other time after the initial days of the 2022 invasion, taking an area half the size of London over the past month.

‘Russia has set new weekly and monthly records for the size of the occupied territory in Ukraine,’ independent Russian news group Agentstvo said in a report this week.

The Russian army captured almost 235 square kilometres (91 square miles) in Ukraine over the past week – a weekly record for 2024 – and had taken roughly 600 square kilometres (232 square miles) in November, the report claimed.

Those figures were largely supported by the US-based Institute for the Study of War, which put the amount of territory gained since November 1 at 574 square kilometres (221 square miles) – an average rate of 22 square kilometres per day.

The war is now entering what some Russian and Western officials say could be its most dangerous phase weeks before Donald Trump returns to the Oval Office amid fears he could dramatically reduce aid to Ukraine as he seeks to force a ceasefire deal.

North Korean troops are reported to be bolstering Moscow’s forces and Kyiv is now using Western-supplied missiles to strike back inside Russia – a development that prompted Putin to unleash a never-before-seen ‘Oreshnik’ hypersonic missile last week.

The thrust of the Russian advance has been in Ukraine’s Donetsk region, with Moscow’s forces pushing towards the town of Pokrovsk and into the town of Kurakhove.

Pokrovsk is widely cited as a key strategic location given that it serves as a vital logistics hub for Ukraine’s Armed Forces.