WARNING: Graphic content 

Ukrainian troops have regained control of the entire region around their capital city, Kyiv, but their victory has been marred by the gut-wrenching scenes left behind in towns previously occupied by Russia. 

Deputy Defence Minister Ganna Maliar announced on Saturday, local time, that Ukraine had taken back the "whole Kyiv region", after Russian troops hastily retreated from areas surrounding the capital. 

"Irpin, Bucha, Gostomel and the whole Kyiv region were liberated from the invader," Maliar said. 

All three towns have suffered heavy destruction in the five weeks since Russia began its invasion, with civilians facing relentless shelling and artillery fire. 

Horrifying images have emerged showing bodies lining the streets of Bucha, with all the victims appearing to be dressed in civilian clothing, 

"All these people were shot, killed, in the back of the head," Mayor Anatoly Fedoruk told AFP. 

Fedoruk said a further 280 victims have already been buried in mass graves across the town. 

The mayor also told Al Jazeera that it had not been possible to collect a further 22 bodies strewn across the street due to fears Russian soldiers may have booby-trapped the corpses with mines. 

Ukrainian presidential adviser Mykhaylo Podolyak shared graphic images of civilians lying dead in the streets of Bucha with their hands tied behind their backs. 

Ukrainian servicemen check streets for booby traps in the formerly Russian-occupied Kyiv suburb of Bucha, Ukraine. Photo / AP 

"These people were not in the military. They had no weapons. They posed no threat. How many more such cases are happening right now in the occupied territories?" he wrote. 

Illia Ponomarenko, a defence reporter with The Kyiv Independent, confirmed people had been "executed" in Bucha. 

"You did it. You are all involved. You allowed it," Ponomarenko told the Russians. 

"In the Kyiv region alone, there are still a lot of cities and villages in ruins and with mountains of corpses on the streets. 

"Live as you wish with this knowledge until the end of your days." 

Survivors have been seen picking through the wreckage of the crumbling town, as Ukrainian troops patrol the streets in tanks bearing the country's flag. 

Soldiers have been handing out food, water and medicine to those that survived the invasion, the first time in more than a month these people have been delivered fresh supplies. 

Ukrainian soldiers and foreign fighters cross a bridge during a clearing-out operation of remaining Russian forces in Irpin, Ukraine. Photo / AP 

Allegations children mutilated, used as human shields 

In a forested area outside of Kyiv, an 80-year-old woman revealed the extent of the horrors committed by Russians ahead of their retreat. 

Maria Dabizhe told The Times Russian forces arrived in her town just a few days into the war. Their explanation when questioned was "We're just trying to do our job". 

Four doors down from Dabizhe's house, her neighbours were found dead, their hands and feet bound together. 

Further down the road, the mutilated bodies of 18 men, women and children were found in a basement, according to territorial defence fighters. 

Witness reports have also emerged of children being used as human shields by Russian soldiers to cover their retreat from areas surrounding Kyiv. 

Ukraine's attorney general is compiling first-hand accounts of claims Russian forces had been using Ukrainian children as cover to ensure they can leave the area safely, The Guardian reports. 

A Ukrainian serviceman takes a selfie photograph standing on a destroyed Russian tank after Ukrainian forces overran a Russian position outside Kyiv, Ukraine. Photo / AP 

There have also been allegations that children were taken as hostages to ensure locals wouldn't hand over information about their movements to Ukrainian forces. 

Ukraine's human rights ombudsman, Lyudmila Denisova, told the publication there were allegations of troops "using children as cover" in Sumy, Kyiv, Chernihiv and Zaporizhzhia Oblast. 

Ukraine Ministry of Defence spokesman Colonel Oleksandr Motuzyanyk said every one of these alleged war crimes will be put before the courts. 

"Russian soldiers have used Ukrainian children as hostages, putting them on their trucks. They're doing it to protect their vehicles when moving," he told The Guardian. 

"There have been cases of brutal behaviour against minors been recorded, documented by a Ukrainian and international institutions, and we'd like to emphasise that information in each and every case will be given to the national criminal courts and the occupiers will be brought to justice for each and every military and war crime they commit." 

Ukrainian servicemen ride on a fighting vehicle outside Kyiv, Ukraine. As Russian forces pull back from Ukraine's capital region. Photo / AP 

Russian retreat part of Putin's new tactic 

Russia now appears to be focusing its military efforts on eastern and southern Ukraine, where it already holds large swathes of territory. 

Military analysts have said the retreat from the Kyiv region isn't a sign of defeat, and instead signals that Putin may be preparing for a new offensive. 

Ukrainian presidential adviser Mykhaylo Podolyak said Moscow's withdrawal from the north meant Russia was now "prioritising a different tactic". 

"Without heavy weapons we won't be able to drive (Russia) out," he said. 

Russia's Deputy Defence Minister Alexander Fomin claimed Russia was withdrawing from Kyiv and Chernihiv to "increase mutual trust and create conditions for further negotiations". 

But this explanation has been met with heavy scepticism from Ukrainian President Volodymyr Zelensky. 

"We know that this is not a withdrawal but the consequences of being driven out," he said. 

"But we also are seeing that Russia is now concentrating its forces for new strikes on Donbas, and we are preparing for this." 

Ukraine estimates more than 20,000 people have been killed since Putin ordered his troops to invade the country on February 24. 

A Ukrainian serviceman secures the retreat of fellow soldiers who checked bodies lying on the street for booby traps in the formerly Russian-occupied Kyiv. Photo / AP 

Countless more have been injured and more than 10 million have been forced to flee their homes. 

While Russia may be preparing to launch a new offensive against Ukraine, Zelensky has declared he will not accept any outcome other than "victory" against Moscow. 

"A victory of truth means a victory for Ukraine and Ukrainians," he told Fox News host Bret Baier. 

"The question is when it will end. That is a deep question. It's a painful question. Besides victory, the Ukrainian people will not accept any outcome." 

Baier then asked what Zelensky was "willing to agree to" in order to secure a peace deal and specifically brought up the possibility of ceding Ukrainian territory to Russia. 

"We do not trade our territory," the Ukrainian President responded. 

"The question of territorial integrity and sovereignty is out of discussion."