UKRAINIAN buildings are being daubed with chilling messages singling them out for attack by Russian airstrikes, sources in Kyiv have claimed.
As Russia continues its military bombardment of Ukraine, Russian forces and pro-Kremlin saboteurs have allegedly been marking buildings to aid Vladimir Putin's troops.
Terrifying pictures show apartment buildings in Kyiv with red crosses on their roofs.
And video shared on Twitter allegedly shows a pro-Russian marking the location of a gas pipe on a high-rise residential building, to allow Moscow's forces to target it for maximum devastation.
Authorities in the city have issued warnings to its citizens to be vigilant for any suspicious symbols.
"Residents of high-rise buildings that have access to the roof, please urgently check the roof for signs," the Kyiv local government said on social media.
"Tags on wood can be either painted or covered with reflective tape," another warning said.
It urged residents to smear such signs with dirt, knock them down, or otherwise cover them.
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Lights tuned to specific coloured frequencies can also reportedly lead missiles and drones down safe "corridors" to avoid interception or obstacles - such as high-rise buildings.
Others placed on the side of a road can direct which vehicles should go where.
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More sinister devices can also act as homing beacons, allowing enemy weapons to silently pinpoint specific targets.
Ukraine's authorities say small transmitters are appearing on significant road intersections and infrastructure facilities.
Such an apparent old-fashioned move is useful in a war where technology is open to sabotage and hacking, such as the jamming of GPS signals, and interception of radio messages.
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A video shared on Twitter shows a mysterious transmitting item with a green flashing light reportedly captured by Ukrainians from the Russians.
The caption reads: "Footage of the device that is used by Russian saboteur units in Ukraine. The light-emitting object has been retrieved by Ukrainian forces.
"These are beacons that are used for either airstrikes, artillery strikes, or for the landing of Russian troops."
Kyiv residents have been using social media to report suspicious activity, and footage of people appearing to place marker pins and UV signs are being widely circulated.
Another short video shared by a Ukrainian news agency filmed from a high rise shows a figure appearing to mark a gas pipe on the side of an apartment building.
"Warning! The saboteurs placed many marks around the city," the video was captioned. "In particular, ballistic. And today Kyivans filmed how gas pipes are marked on apartment buildings. Be vigilant! As soon as you see this, contact the police immediately!"
Residents of high-rise buildings that have access to the roof, please urgently check the roof for signs
Kyiv local government
Kyiv's mayor Vitali Klitschko has urged residents to remain vigilant for any potential symbols springing up to guide Russian missiles.
"City officials are urging citizens to immediately report tagged locations, submit photos to law enforcement, and report suspects who may be involved in tagging," he said at the weekend,
"In Ukraine, in the capital, in particular, the number of detected marks of saboteurs who leave directly on the streets and buildings of both residential buildings and businesses has increased.
"Labels are placed to adjust the fire of the occupying forces of the Russian Federation."
He accused Ukrainian "collaborators" of "treason" and threatened to jail anyone who helped Putin's invaders.
"The crime is punishable by imprisonment for a term of 12 to 15 years with or without confiscation of property."
REFLECTIVE TAGS
Other markers appear to be small reflective tags, with a similar effect as an aircraft transponder - reflecting and amplifying any radar pulse that hits it to stand out among the rubble.
Police in the western Ukrainian city of Lviv have urged residents to use backlights or UV lights to help find fluorescent paint.
They said these markings were "used by Russian agents who have infiltrated the city to direct missile strikes".
Last week, pictures of Ukrainians sheltering in underground stations went viral, as desperate Kyivans tried to escape the Russian blitz.
And there were miraculous scenes when a mother gave birth to her baby daughter in the Kyiv metro.
SABOTEURS PAINTING CROSSES
But not everyone has the option of sheltering in the underground in the city of almost three million people, with many still in their homes.
Kyiv resident Anastasia Russo, 25, has been forced to shelter in her bathroom from the Russian onslaught and says buildings on her street have been marked as targets.
"There is no bomb shelter around this house so my only hope is the bathroom is strong enough to protect me," she told AAP.
Anastasia said she has seen saboteurs painting crosses and circles on her street, as well as roads and buildings across the city to guide Putin's aerial attacks.
"Many people are walking around the streets, even children, looking for these marks... we are doing everything we can to cover them," she said.
Journalist Nika Melkozerova, executive editor of The New Voice of Ukraine, shared a picture from the top of her high-rise apartment building on Twitter.
"Checking our roofs," she wrote. "As our intelligence says saboteurs leave marks for avia strikes on the roofs of high resident buildings in Kyiv.
"Ours is secured by the guy who lives on the roof. It is the first time I met him."
Anastasia, who is from a Russian-speaking family, says she has been preparing sandbags and making fuses for Molotov cocktails, as well as fighting Russian disinformation on social media.
"Russia says they do not attack civilians - that's a lie," she said.
"Our religion is freedom and dignity, that's why I believe we will win."
It comes amid fears Russia will unleash an "indiscriminate" bombing campaign after President Putin's hopes of a quick, simple invasion were dashed.
UK defence secretary Ben Wallace warned Russia's offensive - which is entering its fifth day - could become even more violent as Putin's forces find themselves humiliatingly bogged down in a series of skirmishes across Ukraine.
In a possible sign of this more reckless military strategy, a six-year-old girl was killed in a Russian airstrike in the eastern Ukrainian city of Mariupol.
Horror images show the little girl wearing unicorn pajamas being rushed to hospital in an ambulance.
A furious doctor who tried in vain to save her life told a reporter: "Show this to Putin. The eyes of this child, and crying doctors."
Another girl, thought to be nine or 10 and named only as Polina, was reportedly killed alongside her parents in Kyiv after Russian troops opened fire on her family's car.
Her brother is currently at Okhmatdyt children's hospital, while her sister is intensive care, the city's deputy mayor Volodymyr Bondarenko said.
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Ukraine's President Volodymyr Zelenskyy has warned the country faces a "crucial 24 hours" as Russia continues to bombard him, ahead of crucial peace talks in Belarus.
Belarusian President Alexander Lukashenko, a close ally of Putin, has accused the West of pushing Russia to the brink of World War 3 after Moscow put its nuclear forces on "high alert".