Russia, due to fierce resistance from the Ukrainian military, has failed to achieve its first-day objectives and lost territory it had earlier captured but heavy fighting continues.

Britain has reassured NATO members "that if one Russian boot lands on NATO soil, military force will be met by military force".

Ukrainian President Zelenskiy has called on 'all citizens who were ready to defend the country from Russian forces' to come forward, saying weapons would be given to anyone who wants them.

At around 3am this morning, Russian forces began a massive assault into Ukraine - here's a summary of what's been happening.

At 6am Moscow time, Russian President Vladimir Putin announced a military operation to invade Ukraine; minutes later, missile strikes began at locations across the country including near the capital Kyiv.

Europeans are "waking up to a very dark day" said British minister Sajid Javid as tanks and armoured vehicles were seen overnight near Donetsk in eastern Ukraine.

The Ministry of Defence has published its plans for the next 10 years of British military equipment spending.

Additional British forces are heading to Estonia as part of the UK's contribution to strengthening Eastern Europe amid tensions with Russia.

Britain is moving an army battlegroup, Apache attack helicopters, fighter jets and warships to Eastern Europe due to tensions with Russia.

British Army Apache attack helicopters recently conducted cold-weather training in Norway during Exercise Clockwork.