A Russian invasion of Ukraine could happen at any moment, a defence minister has warned.

Armed Forces Minister James Heappey has described the massing of roughly 130,000 Russian troops along the Ukrainian border as a "credible force set to do something imminently".  It comes after Defence Secretary Ben Wallace compared diplomatic efforts to prevent a Russian invasion of Ukraine to appeasement as he said it is "highly likely" Vladimir Putin will order an attack despite the concerted talks to avert war.

The UK Defence Secretary said there were individuals already in Ukraine "linked to the Russian state in ways that are not conventional".

Russia may already have personnel in place in Ukraine to assist with an invasion, the UK Government believes. Defence Secretary Ben Wallace told MPs there were individuals already in Ukraine "linked to the Russian state in ways that are not conventional" and "that should give cause for concern". He added: "We are becoming aware of a significant number of individuals that are assessed to be associated with Russian military advance force operations that currently are located in Ukraine."

It comes as concerns over a potential Russian invasion into Ukraine continue to increase. Moscow has massed an estimated 100,000 troops near the border with Ukraine. Mr Wallace told the Commons Foreign Affairs Committee that any incursion into Ukrainian territory would be unacceptable. He said: "Any crossing into Ukraine, whether small or large, would be viewed as a breach of that sovereignty, against international law and an invasion. "You can't be half-pregnant, you are either invading a country or you are not."

Coordinated suicide bomb blasts at Kabul airport on Thursday have left at least 170 dead and many more injured.

Isis-K has claimed responsibility for the attack, which targeted US troops and Afghans attempting to secure the last remaining places on military evacuation flights out of the country.

On Friday, the US said it killed a "planner" for the group in an air strike in Afghanistan.

The threat of further attacks around Kabul Airport will increase as Western troops get closer to leaving the country, Defence Secretary Ben Wallace said on Friday, with Isis-K hoping to show it drove foreign troops from Afghanistan.

"The threat is obviously going to grow the closer we get to leaving," he told Sky News. "The narrative is always going to be, as we leave, certain groups such as ISIS will want to stake a claim that they have driven out the US or the UK." 

On Thursday night, President Joe Biden pledged to "hunt down" the attackers and ordered his military to plan strikes.

He said: "Know this: we will not forgive, we will not forget. We will hunt you down and make you pay." 

Here we look at how Isis-K came to exist and why it poses such a threat to US forces in Afghanistan.