Russia is continuing to move forces towards the border with Ukraine despite claims by Moscow that it is pulling back, Britain’s head of military intelligence has warned.

Lieutenant General Sir Jim Hockenhull, the Chief of Defence Intelligence, said there have been sightings of additional armoured vehicles, helicopters and a field hospital heading to the border zone.

His stark warning came after Nato defence ministers meeting in Brussels said they had seen no evidence to support Russia’s claims it had begun withdrawing troops to their bases.

In a statement issued by the Ministry of Defence, Gen Hockenhull said: “Contrary to their claims, Russia continues to build up military capabilities near Ukraine.

“This includes sightings of additional armoured vehicles, helicopters and a field hospital moving towards Ukraine’s borders. Russia has the military mass in place to conduct an invasion of Ukraine.”

Earlier, alliance defence ministers said they remained “gravely concerned” by the Russian military build-up and again urged the Kremlin to revert to the “path of diplomacy” in line with its international commitments.

Secretary general Jens Stoltenberg said Nato was considering establishing new battlegroups in central, eastern and south-eastern Europe to counter the threat from Moscow, which he described as “the new normal”.

Russia has repeatedly denied that it has any intention of attacking Ukraine, despite massing an estimated 130,000 troops along the border with its southern neighbour.

Mr Stoltenberg said that while they welcomed signs Moscow was prepared to continue with diplomacy, Nato they had not seen any signs of de-escalation on the ground.

“What we see today is that Russia maintains a massive invasion force ready to attack, with high-end capabilities from Crimea to Belarus. This is the biggest concentration of forces in Europe since the Cold War,” he said.

“Moscow has made it clear that it is prepared to contest the fundamental principles that have underpinned our security for decades, and to do so by using force. I regret to say that this is the new normal in Europe.”

The warning came after the Russian defence ministry issued video footage which it said showed armoured vehicles moving across a bridge away from Crimea, the peninsula Moscow annexed from Ukraine in 2014.

While Western allies have made clear they will not intervene militarily in Ukraine – which is not a Nato member – they are looking to shore up their defences elsewhere in eastern Europe.

Britain has already said it is doubling the number of troops in Estonia while sending 350 Royal Marine commandos to Poland.

Four additional RAF Typhoon jets are heading to Cyprus to join Nato patrols over eastern Europe while offshore patrol vessel HMS Trent will shortly be joined in the eastern Mediterranean by HMS Diamond, a Type 45 destroyer.

Defence Secretary Ben Wallace, who has been attending the meeting in Brussels, said: “Alongside our Nato allies, we are deploying troops and assets on land, sea and air to bolster European defences in response to the build-up of Russian military forces on the border of Ukraine.

“Nato and our allies have been clear that an invasion of Ukraine will be met with severe consequences. De-escalation and diplomacy remain the only path out of this situation.”

Boris Johnson discussed the crisis in a call with United Nations secretary-general Antonio Guterres, in which they agreed an invasion of Ukraine would have “catastrophic and far-reaching consequences”.

“They agreed to continue working closely together to pursue an urgent diplomatic resolution and avert a disastrous military escalation and humanitarian crisis.” A No 10 spokesman said.

The Prime Minister has warned that Russia will face “very tough” new sanctions if it invades Ukraine, but Moscow’s foreign minister Sergei Lavrov said the UK would face reciprocal action if that happened.

“Sanctions could be imposed against any legal entities and individuals just for being Russian,” Mr Lavrov claimed about the UK plans at a press conference in Moscow.

Warning against a new round of “sanction wars”, he said: “Both the Russian government and our parliament, they won’t be idle when they see such things are happening in the West.”

In Ukraine, a “day of national unity” was being marked on the day some analysts had predicted an invasion would take place.

President Volodymyr Zelensky said in a video address to the nation: “We can defend our home only if we stay united.”

Although no invasion has been launched, the country was hit by a cyberattack which targeted its defence ministry and banks on Tuesday.

Russian foreign ministry spokeswoman Maria Zakharova mocked the West over suggestions an invasion could take place on Wednesday.

She added: “Even the withdrawal of a number of Russian units to their permanent duty stations after the end of the exercises was presented as a cunning manoeuvre designed to divert attention from the impending invasion.”