Kiev, Mar 11 (IANS): Mayor of Kiev Vitaliy Klitschko said that the Ukrainian capital has become a "fortress" being defended by armed civilians, while half of the city's entire population have left amid the looming threat of a Russian invasion.

"The key goal of the Russians is to capture Kiev, to surround Kiev, to take it in a ring, then to attack and overthrow the government. Their plans are not being realised, thanks to our guys in Bucha, Vorzel, Irpen and Gostomel, where fierce fighting is taking place... Our guys are thwarting all plans to surround Kiev," the Mayor said in a video address on Thursday night.

According to the latest estimates, every second Kiev citizen has left, he said, adding that under 2 million residents are now living in the Ukrainian capital.

Nevertheless, Kiev has now become a "fortress", Klitschko was quoted as saying in the video by the Ukrayinska Pravda newspaper.

The Mayor also reaffirmed that authorities in Kiev continue to ensure the livelihood of the city.

"The utility services are working. Warm, water, light, internet in the capital is. Most pharmacies and grocery stores operate.

"The city provides passenger transport. Kiev rescuers meet people at the railway station. And those who want to leave Kiev are sent by trains to Western Ukraine," he added.

Klitschko further noted that musicians and other professionals have joined the territorial defence, reports Ukrayinska Pravda.

"There has never been such a spirit! Everyone says, 'nothing will happen, we will not surrender our city'. I can repeat these words: the city stood, the people will stand. They won't give up. And the enemy won't pass."

The Mayor's remarks came as a senior US defence official said that Russian forces have moved about 5 km closer to Kiev in the past 24 hours, which means the troops were now just 15 km from the city centre, the BBC reported.