BORIS Johnson has again ruled out imposing a no-fly zone over Ukraine, despite Russia’s strike on a maternity hospital in the besieged city of Mariupol.

The attack on Wednesday was said to have killed three people, including a child, and injured 17 others. It led to renewed calls from President Volodymyr Zelenskyy for Western warplanes to intervene.

However, Johnson said that while Vladimir Putin had abandoned “all norms of civilised behaviour”, a no-fly zone would bring the UK and Nato into direct conflict with Russia – something he was determined to avoid.

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Speaking on Sky New’s Beth Rigby Interviews, he acknowledged that some of his conversations with Zelenskyy had been “deeply upsetting” as the Ukrainian leader appealed for more help.

He said: “What’s happened in Mariupol in that maternity hospital really shows that Putin is prepared just to reject, to abandon, all norms of civilised behaviour.

“The difficulty is that there is a line beyond which, quite frankly, the UK and Nato would be deemed to be in conflict – direct conflict – with Russia.

“It’s agonising. It’s absolutely agonising. And I’ve had this conversation at least a couple of times now with Volodymyr, but I think the difficulty is that it will require me to order RAF jets, UK pilots into the air with a mission to shoot down Russian fast jets.

The National:

Johnson (right) with Defence Secretary Ben Wallace (left)

“I think we’ve got to be realistic… there’s a line that is very difficult to cross.”

Johnson said the he believed the conflict would only end when Mr Putin accepted he had made “a disastrous miscalculation” and withdrew his forces.

The PM said: “I don’t think that he can conquer Ukraine. Ukraine is a country of 45 million people.

“The best way out for Russia, for the Russian people, is for withdrawal of the Russian forces and for total cessation of hostilities.

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“Vladimir Putin has himself made it very difficult to find an off ramp, and he has, I think, driven his tank, so to speak, down a cul de sac from which it will be very hard to extricate himself but he must.

“I can’t see a way out that doesn’t begin with the realisation by the Kremlin, that they made a catastrophic mistake and that it’s time to begin to withdraw it, and to withdraw immediately.”

It comes as Scotland Secretary Alister Jack was accused of "pathetic and patronising politicking" after he said Nicola Sturgeon's comments regarding a no fly-zone over Ukraine were "naive and irresposible".

The First Minister had said that she shares concerns over a direct military confrontation between Russia and Nato but that a no-fly zone and other options should be "considered on a daily basis".