If Russian soldiers were in any doubt where their country was on the map, they can rest a bit easier now.

In response to claims that Vladimir Putin's troops stumbled into Ukraine 'by mistake', Canadian NATO officials have posted a mocking tweet complete with a primary school-style geography lesson.

The message contains a rather helpful map which is colour-coded and marked in block letters to clearly show that Ukraine was 'NOT RUSSIA' and that Russia was indeed 'RUSSIA'.

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Canadian officials at NATO posted this sarcastic tweet with a map showing that Ukraine was 'NOT RUSSIA' and that Russia was 'RUSSIA' in response to claims that Russian soldiers found themselves in Ukraine by mistake

In a further broadside at the Russian president, the area marked 'NOT RUSSIA' includes the Crimea peninsula, which was controversially annexed by Moscow in March.

In a message dripping with sarcasm, the tweet said: 'Geography can be tough.

'Here's a guide for Russian soldiers who keep getting lost & "accidentally" entering #Ukraine.'

It came in response to claims by the Kremlin that ten paratroopers captured in Ukrainian territory earlier this week had accidentally crossed the border because it was 'poorly marked'.

The version was widely disbelieved in Kiev, which claims it has faced repeated attacks from Kremlin troops in a conflict which has seen almost 2,300 deaths.

The crisis in Ukraine escalated further today when president Petro Poroshenko accused Russia of a military invasion.

Prisoners: These pictures show two of the ten Russian paratroopers who claimed they entered Ukraine by accident because the border was poorly marked, a version which is being mocked by Canadian NATO officials

The Kiev leader - who changed his plans shortly before leaving Kiev's Boryskil airport - demanded an urgent meeting of the UN security council as one senior aide called on him to impose martial law.

'The Russian Federation's troops have entered Ukraine,' said Poroshenko less than two days after shaking hands with Vladimir Putin on a peace roadmap.

'The world must give an assessment of the sharp aggravation of the situation in Ukraine,' he said.

'I have taken the decision to cancel the visit to Turkey due to the sharp deterioration of the situation in the Donetsk region, particularly in Amvrosiyivka and Starobesheve, as Russian troops have been sent into Ukraine.'

Ukraine's president Petro Poroshenko (left) today accused Vladimir Putin (right) of a military invasion as he abruptly cancelled a trip to Turkey to meet his top security officials

Poroshenko urgently summoned a meeting of his National Security and Defence Council.

Senior Interior Ministry adviser Anton Heraschenko warned: 'The incursion of Putin's Russian Federation regular army into Ukraine is an accomplished fact.'

He claimed there was a need for martial law in Ukraine and urged EU countries to halt buying Russian oil, gas, timber and other natural resources, and also to discontinue granting of any credits, and freeze Russian state companies' assets in the EU.