Ukrainian buildings are reportedly being marked with mystery symbols which pinpoint them for attack by Russian airstrikes, sources in Kyiv have said.
Russian forces and pro-Kremlin saboteurs have allegedly been marking buildings with the chilling messages to aid Vladimir Putin ’s troops.
It comes as Russia continues its attack on Ukraine, with Putin having ordered part of his nuclear forces to be on enhanced combat duty in an alarming escalation of tensions.
Alarming images show apartment buildings in Kyiv with red crosses on their roofs, presumably marking them for airstrikes.
According to Sun Online reports, footage shared on Twitter allegedly shows a pro-Russian marking the location on a high-rise residential building, to allow Moscow’s forces to target it for maximum impact.
Authorities in Kyiv are urging its citizens to be vigilant for any suspicious symbols or marks.
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"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.
Residents are being urged to smear such signs with dirt, knock them down, or otherwise cover the marks up.
Other sinister gadgets believed to be being used by Russian forces included homing transmitters allowing enemy weapons to silently pinpoint specific targets - which Ukrainian authorities say are appearing on significant road intersections.
A video shared on social media depicts a mysterious transmitting item with a green flashing light, which was reportedly captured by Ukrainians from the Russians.
A 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."
Suspicious activity has been reported by Kyiv residents on social media, with footage of people appearing to place marker pins and UV signs being widely circulated.
A Ukrainian news agency has also shared a short video filmed from a high rise, showing a figure appearing to mark a gas pipe on the side of an apartment building.
A caption accompanying the video reads: "Warning! The saboteurs placed many marks around the city.
"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!"
Vitali Klitschko, Kyiv’s mayor, has urged residents to remain vigilant for any potential symbols springing up to guide Russian missiles and report suspicious activity they do see.
He has also accused Ukrainian collaborators of "treason" and threatened to jail anyone who helped Putin’s invaders.
Other suspected markers are small reflective tags, which were believed to have a similar effect to an aircraft transponder, in reflecting and amplifying any radar pulse that hits it to stand out among the rubble.
Police have urged residents in the western Ukrainian city of Lviv to use backlights or UV lights to help them detect fluorescent paint.
These markings were used by Russian agents who had infiltrated the city to direct missile strikes, they said.
Warnings about the old school war tactics come as satellite imagery has highlighted a large deployment of Russian ground forces including tanks moving in the direction of Kyiv.
The images released by Maxar Technologies Inc showed a deployment comprised of hundreds of military vehicles.
The convey was situated northeast of the Ukrainian city of Ivankiv and contained fuel, logistics and armoured vehicles including tanks, infantry fighting vehicles and self-propelled artillery.
Russian artillery bombarded residential districts of Ukraine's second-largest city Kharkiv on Monday, killing possibly dozens of people, Ukrainian officials said.
Moscow's invading forces however met stiff resistance from Ukrainians on the fifth day of conflict.
The attacks took place while Russian and Ukrainian officials met on the Belarusian border, but their talks made no breakthrough.
Russia also faced deepening isolation and economic turmoil as Western nations, united in condemnation of its assault, hit it with an array of sanctions that rippled around the world.
