WARNING: GRAPHIC CONTENT
Radio messages which prove Russian forces deliberately murdered Ukrainian civilians in Bucha have reportedly been intercepted by German intelligence.
The intercepted messages could play a key role in establishing that Russia committed war crimes in Ukraine.
Russian soldiers openly discuss the killings in the recordings, according to details leaked to Spiegel magazine.
In one instance, a Russian soldier says he has just shot a cyclist. The description matches pictures and video from the town.
One video recorded during the fighting shows two armoured vehicles opening fire on a cyclist. A second video shot after Russian forces withdrew shows the dead body of a cyclist wearing the same clothes.
In a second recording obtained by German intelligence, a Russian can be heard ordering: "Question the soldiers first, then kill them".
Separately Ukrainian intelligence released what it said was an intercept of Russian communications in which soldiers are ordered to kill civilians.
In the recording, a Russian soldier can be heard reporting there are civilians in the area and is ordered: "Kill them all."
"What are you waiting for, you a--- f------?" the officer asks.
"This is a whole village of civilians," the soldier replies.
"Shoot the civilian cars," the officer says. It is not clear where the alleged incident took place.
If confirmed, the recordings would refute Russia's attempts to claim its troops were not behind the killings in Bucha and elsewhere, or that they were "staged" by the Ukrainian government.
They would also indicate the killings were systematic and deliberate and could prove crucial in any future war crimes prosecution.
"Radio intercepts by German intelligence show that the massacre of civilians in Bucha was not accidental or actions of rogue soldiers. Russian occupiers talk about atrocities in their daily routine," the Ukrainian ministry of defence tweeted.
"Almost 90 per cent of the murdered civilians in Bucha were found to have bullet wounds, not shrapnel ones ... They are not random collateral casualties of war. They were killed deliberately, on purpose."
The existence of the messages intercepted by Germany's BND foreign intelligence service emerged in a classified briefing to a parliamentary committee, details of which were leaked to Spiegel.
The recordings also appear to indicate the "Wagner Group" paramilitary organisation played a role in the killings at Bucha, according to the report.
No details are given but the Wagner Group has been active in Ukraine for many years.
Ostensibly a private mercenary company, it has repeatedly been deployed alongside Russian forces.
It has been accused of war crimes in Ukraine, Syria and elsewhere and Vladimir Putin is believed to use it to distance official Russian forces from his more extreme actions and provide plausible deniability.
Eyewitness reports from Bucha described how Russian tactics became more brutal when young soldiers involved in early fighting in the town were replaced by new units.
It is believed this could be evidence of a deliberate strategy of using specialist units to sow terror by targeting civilians. Some witnesses described the new arrivals as Chechens.
The scale of killing in Bucha emerged last weekend when Russian forces withdrew, leaving the streets littered with the bodies of civilians.
The BND has more disturbing recordings of intercepted radio messages which appear to indicate further Russian atrocities in other locations which have yet to emerge, according to the report.
The intelligence service is analysing the recordings to determine the whereabouts of the killings they describe.
Some are believed to suggest similar war crimes may have been committed in and around the besieged city of Mariupol.
The port city on the coast of the Sea of Azov has seen some of the most intense Russian bombardment of the war.
Simone White, 28, is the fifth tourist to have died after becoming ill last week.