Fortifications were frantically dug in Kyiv to block the Russian military advance, BBC reported.

Russian troops are in the north of the capital Kyiv, Ukraine authorities said, with videos showing a steady advance of armoured vehicles.

At least 25 civilians have been killed and 102 injured in airstrikes across country, the United Nations said. Images showed a missile fired by Russia hitting a residential area in Bucha in the northewest of Kyiv.

Amid conflicting claims by Ukraine that its forces were battling the Russians, British Defence Secretary Ben Wallace said that Moscow had lost 450 military personnel.

Earlier, the Ukrainian Defence Force called for civilian recruits regardless of age.

Defence Minister Alexey Reznikov said: "I decided, in agreement with the Commander of the Troops of the Armed Forces of Ukraine ... to involve (those) over 60 years old, who are morally and physically ready to resist and defeat the enemy".

Meanwhile, a special train with 7,000 people left Kyiv to the country's western cities to be away from the heavy fighting.

(With UNI inputs)