KYIV - CBS News senior foreign correspondent Charlie D'Agata and his team have grown accustomed to the sounds of explosions and air raid sirens after weeks in Ukraine's capital. But on Tuesday, they were rattled awake around 5 a.m. as the ground shook. The Russian military machine again turned its guns on Kyiv overnight, raining artillery down on residential neighborhoods.
Pre-dawn explosions thundered in and around the city, with one strike on an apartment building killing at least four people, according to Mayor Vitali Klitschko. It was one of the heaviest bombardments since the invasion began. Klitschko declared a curfew from Tuesday night until Thursday morning.
He's estimated that more than half of Kyiv's 3 million inhabitants have already fled to safer regions or left the country altogether. The United Nations said Tuesday that 3 million people have left Ukraine seeking shelter in neighboring nations — Europe's biggest refugee crisis since the Second World War.
Others have taken up semi-permanent residence deep inside Kyiv's subway system, some even sleeping in trains.
In the wooded outskirts of the city, Ukrainian soldiers have dug in. Ukraine's Defense Ministry released video showing off their presence, with anti-tank weapons and mortars. The video was reassurance for fellow Ukrainians and a clear warning for Russians. D'Agata and his team have seen for themselves, however, that the defense buildup in and around Kyiv is not merely for show.
Every single road is barricaded and manned by troops, reserves or volunteers.
Among them, 32-year-old Volodymyr, an economist who just a few years ago was living and working in Washington D.C.
"We are ready for them," he told CBS News. "You know, in Ukraine, we tell who comes to us, will die here."
He said the blood of invaders would be good for Ukraine's soil.
At a local auto repair shop, D'Agata said it was like "MacGyver" meets "Mad Max" as he met Oleg, who was busy modifying weapons ripped off ruined Russian armored vehicles for use by Ukrainian fighters.
Oleg said the work made him happy, as every weapon that comes in for him to work on is one more barrel pointing at Russian forces, rather than at Ukraine's people.
In an overnight address, President Volodymyr Zelensky made an appeal directly to Russian soldiers: "On behalf of the Ukrainian people, I give you a chance, a chance to survive" he said. "If you surrender to our forces, we will treat you the way people are supposed to be treated — as people, decently."
Despite days spent flattening suburbs like Irpin and Bucha with missiles and artillery — shelling that resumed overnight — Russia's ground forces have yet to advance to the capital. American officials believe they're within about 10 miles, but analysts say the approach has been slowed by logistical shortcomings and fierce Ukrainian resistance.
Many in Kyiv fear the capital is now just awaiting the same fate as other Ukrainian cities closer to Russian territory, like Mariupol.
The key port town has suffered from the full fury of Russian firepower for days. There was a glimmer of hope Monday as city officials confirmed some of the first civilian evacuations under a cease-fire agreed with Russia. But only around 160 vehicles were said to have left, and there are an estimated 400,000 people trapped in Mariupol, where food, water, heating and electricity supplies were cut days ago.
Russian forces unleashed new artillery strikes in Kharkiv, meanwhile, in the northeast, in their ongoing effort to capture Ukraine's second-largest city.
The tactic is clear, and it is familiar from Russia's brutal campaign alongside dictator Bashar Assad in Syria: Where Russian forces encounter resistance and can't, or won't, quickly move in and seize a city, they surround it, and destroy it from afar.
Across the country, Ukraine's tenacious forces refuse to give up ground. But its cities are increasingly under siege, and its civilians are paying a heavy price.
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