Prime minister Boris Johnson has said Russia's invasion of Ukraine "must end in failure".

On Thursday (February 24) Russia president Vladimir Putin announced a "special military operation" in the country's Donbas region which has sparked global response.

Having denied plans to invade Ukraine for months, Mr Putin announced the action during a televised address early on Thursday morning, saying the move was a response to threats from Ukraine.

Having chaired an urgent Cobra emergency committee meeting on Thursday morning, Mr Johnson addressed the nation in an address at midday.

He said: “A vast invasion is under way by land, by sea and by air. And this is not, in the infamous phrase, some faraway country of which we know little.

“We have Ukrainian friends in this country, neighbours, co-workers. Ukraine is a country that for decades has enjoyed freedom and democracy, and the right to choose its own destiny.

“We and the world cannot allow that freedom just to be snuffed out. We cannot and will not just look away.”

Mr Johnson said the “hideous and barbaric venture” of Russian President Vladimir Putin “must end in failure”.

He said: “It’s because we’ve been so alarmed in recent months at Russian intimidation that the UK became one of the first countries in Europe to send defensive weaponry to help the Ukrainians.

“Other allies have now done the same and we will do what more we can in the days ahead.

“Today, in concert with our allies we will agree a massive package of economic sanctions designed in time to hobble the Russian economy. And to that end, we must also collectively cease the dependence on Russian oil and gas that for too long has given Putin his grip on Western politics.

“Our mission is clear. Diplomatically, politically, economically, and eventually, militarily, this hideous and barbaric venture of Vladimir Putin must end in failure.”

Mr Johnson added the Putin regime would be condemned to “pariah status” after unleashing a “tidal wave of violence” against Ukraine.

In his address to the nation, the prime minister said the UK stood with Ukraine in its “moment of agony”.

“I say to the Ukrainians in this moment of agony, we are with you. We are praying for you and your families, and we are on your side,” he said.

“If the months ahead are grim and the flame of freedom burns low, I know that it will blaze bright again in Ukraine.

“For all his bombs and tanks and missiles, I don’t believe the Russian dictator will ever subdue the national feeling of the Ukrainians and their passionate belief that their country should be free.”

Mr Johnson concluded by adding: “I say to the British people, and all who have heard the threats from Putin against those who stand with Ukraine, we will, of course, do everything to keep our country safe.

“We will work with them, for however long it takes, to ensure that the sovereignty and independence of Ukraine is restored.

“Because this act of wanton and reckless aggression is an attack not just on Ukraine, it’s an attack on democracy and freedom in eastern Europe, and around the world.

“This crisis is about the right of a free, sovereign, independent European people to choose their own future.

“That is a right that the UK will always defend.”

Mr Johnson's statement came after the Ukraine president Volodymyr Zelensky declared martial law and urged people to stay indoors, amid reports of missile strikes and explosions across the country.

Explosions could be heard in the Ukrainian capital of Kyiv shortly after Mr Putin’s address, while explosions were also reported in the cities of Odesa and Kharkiv.

Ukraine’s border guard agency said the Russian military attacked the country from neighbouring Belarus.

Ursula von der Leyen, president of the European Commission, accused Mr Putin of “bringing war back to Europe”.

Mr Zelensky called on Ukrainian nationals to volunteer for the resistance effort.

He said: “We will give weapons to anyone who wants to defend the country. Be ready to support Ukraine in the squares of our cities.

“We will lift sanctions on all citizens of Ukraine who are ready to defend our country as part of territorial defence with weapons in hands.

“We have severed diplomatic relations with Russia. For all those who have not yet lost their conscience in Russia, it is time to go out and protest against the war with Ukraine.”

Mr Putin said Russia does not have a goal to occupy Ukraine, but the responsibility for bloodshed lies with the Ukrainian “regime”.

The Russia President also warned other countries that any attempt to interfere with the Russian action would lead to “consequences they have never seen”.

Mr Putin accused the US and its allies of ignoring Russia’s demand to prevent Ukraine from joining Nato and offer Moscow security guarantees.

He said the Russian military operation aims to ensure a “demilitarisation” of Ukraine, adding that all Ukrainian servicemen who lay down arms will be able to safely leave the zone of combat.

Mr Johnson said Mr Putin has “chosen a path of bloodshed and destruction” with his attack on Ukraine and that the UK and its allies would respond “decisively”.

In a tweet on Thursday morning, Mr Johnson said he had spoken with Ukrainian President Volodymyr Zelensky to discuss “next steps”.

He said: “I am appalled by the horrific events in Ukraine and I have spoken to President Zelensky to discuss next steps.”

“President Putin has chosen a path of bloodshed and destruction by launching this unprovoked attack on Ukraine.

“The UK and our allies will respond decisively.”