Russia appears to be targeting military infrastructure in early strikes with explosions reported at airfields, military headquarters and military warehouses

• Russia-Ukraine crisis: live updates

Russian forces have unleashed an attack of Ukraine on the orders of Vladimir Putin, who announced a “special military operation” at dawn, amid warnings from world leaders that it could spark the biggest war in Europe since 1945.

Within minutes of Putin’s short televised address, at about 5am Ukrainian time, explosions were heard near major Ukrainian cities, including the capital, Kyiv.

Ukraine crisis has thrust Denis Pushilin and Leonid Pasechnik into centre of events, amid claim they are puppets of Putin

• Ukraine crisis: live updates

For many Russians, it was an unfamiliar sight to see the faces of the two leaders of the pro-Kremlin proxy states in eastern Ukraine pop up on their television screens last Friday, announcing the mass evacuation of Donbas citizens to Russia.

Since then, however, Denis Pushilin and Leonid Pasechnik, heads of the self-proclaimed republics in Luhansk and Donetsk, have seen their political profiles rocket, culminating on Monday with the two leaders asking the Russian president, Vladimir Putin, to recognise their “republics”.

Kyiv mobilises reserves and advises estimated 3 million people to depart in latest sign it believes Putin plans to invade

• Ukraine crisis: live updates

Ukraine has declared a state of emergency, mobilised reserves and told nearly 3 million of its citizens to leave Russia, as the US warned that Vladimir Putin had assembled almost 100% of the forces needed to launch a large-scale invasion of the country.

As Russian diplomats evacuated their embassy in the capital, the Ukrainian government said a massive cyber-attack had targeted ministries and banks on Wednesday. Officials have warned that Russia could use elements of hybrid warfare to sow confusion before launching an all-out military assault.

Vladimir Putin has said Moscow is ready to look for 'diplomatic solutions' over Ukraine, but stressed that Russia’s interests were non-negotiable.

In a video address on Wednesday morning, the Russian president said his country would continue to develop state-of-the-art weapons.

His speech follows Russia’s unanimous approval to deploy 'peacekeepers' to two self-proclaimed republics in Luhansk and Donetsk now recognised by Moscow as independent

• Ukraine crisis: live updates

Analysis: advance forces’ battle readiness will quickly degrade, giving Putin only days to choose invasion or retreat

• Ukraine crisis: live updates

Russian forces massing near Ukraine’s borders can only remain in position for a few days before they have to be sent back to nearby bases or risk their capability being significantly degraded, western officials and experts believe.

That means that President Vladimir Putin will come under increasing pressure to use them in a full invasion of Ukraine – or send them back to staging areas, still in Russia’s south or west, but tens or even hundreds of kilometres back.