THE Russian invasion of Ukraine has begun, a UK Cabinet minister has warned as Boris Johnson vowed tougher sanctions on the Kremlin.

The Prime Minister warned Vladimir Putin appears “bent on a full-scale invasion” as he vowed to swiftly introduce the “first barrage” of sanctions against Russia as other western nations did likewise.

Johnson was briefed in an early morning Cobra committee meeting on the latest intelligence after Putin sent troops into the Donetsk and Luhansk regions, which he has now recognised as independent states.

Health Secretary Sajid Javid warned: “We are waking up to a very dark day in Europe and it’s clear from what we have already seen and found out today that the Russians, President Putin, has decided to attack the sovereignty of Ukraine and its territorial integrity.”

The Health Secretary told Sky News: “We have seen that he has recognised these breakaway eastern regions in Ukraine and from the reports we can already tell that he has sent in tanks and troops.

“From that, you can conclude that the invasion of Ukraine has begun.”

The European Union and the United States are also imposing sanctions in response to the crisis, with Germany announcing the most significant yet. Chancellor Olaf Scholz said his government is cancelling the undersea Nord Stream 2 pipeline, designed to carry natural gas directly from Russia.

The UK Cobra meeting follows an emergency session of the UN Security Council where the UK’s ambassador Dame Barbara Woodward said Russia has “brought us to the brink”, warning that the country’s actions “will have severe and far-reaching consequences”.

She said an invasion would unleash “the forces of war, death and destruction” on the people of Ukraine.

“The humanitarian impact will be terrible on civilians fleeing the fighting. We know that women and children will suffer most.”

The National: Ukraine Tensions Photo Gallery

READ MORE: David Pratt: Russia-Ukraine endgame could be where it all began

She said the Security Council must be united in calling on Russia to “de-escalate immediately”, as well as “condemning aggression against a sovereign nation and defending the territorial integrity of Ukraine”.

“Russia has brought us to the brink,” she said. “We urge Russia to step back.”

The Kremlin claimed Russian forces will “maintain peace” in eastern Ukraine.

After chairing the emergency meeting of the Cobra committee, Johnson said he would later reveal sanctions against entities in Russia and the Donbas.

“This is I should stress just the first barrage of UK economic sanctions against Russia because we expect I’m afraid that there is more Russian irrational behaviour to come,” he told broadcasters.

“I’m afraid all the evidence is that President Putin is indeed bent on a full-scale invasion of the Ukraine, the overrunning, the subjugation of an independent, sovereign European country and I think, let’s be absolutely clear, that will be absolutely catastrophic.”

Following the meeting, the Prime Minister will have calls with other world leaders and will update MPs on the sanctions package at around 12.30pm.

On Monday night Johnson outlined his “grave concern at recent developments in the region” in a call with the Ukrainian president and said he would consider further “defensive support”.

Downing Street said Johnson told President Zelensky that he would “explore sending further defensive support to Ukraine” at the request of the country’s government.

Later, Zelensky told his nation “we are not afraid of anyone” after Russia recognised the independence of the separatist regions.

Foreign Secretary Liz Truss tweeted about the new sanctions from the UK on Monday evening after saying Putin’s actions could not be allowed to go “unpunished”.

SNP Westminster leader Ian Blackford commented: "The West must present a united front in the protection of Ukraine and urge Russia to drawback from their invasion. We all must stand with the Ukrainian people."