A Russian drone approaches for an attack on Kyiv on Monday 2022. The "kamikaze" drones offer financial and strategic advantages to Russia. Photo: AFP/ Yasuyoshi Chiba
On Monday, the residents of an ageing apartment block in central Kyiv bore the brunt of Russia's latest weapon of choice.
The weapons are so noisy that some Ukrainians have nicknamed them "mopeds" for the loud whirring noise their engines make as they fly overhead.
Ukraine officials have called them "kamikaze" drones.
But what exactly are these drones, and why are they quickly surpassing missiles as Russia's weapon of choice?
What are they, and why are they called 'kamikaze' drones?
Ukrainian leaders have accused Russia of using the Iranian-made Shahed-136 "kamikaze" drones, a type of aerial weapon.
Russia has rebranded them Geran-2.
Packed with explosives, they are preprogrammed with a target's GPS coordinates.
They fall into the category of a "loitering munition" because of their capability to loiter overhead before nosediving in for the kill.
The term kamikaze comes from Japan's World War II-era kamikaze pilots, who would fly their explosive-laden aircraft into US warships and aircraft carriers during the war in the Pacific.
A policeman fires at an incoming drone in Kyiv on Monday Photo: AFP/ Yasuyoshi Chiba
How do they work?
The Geran-2 are known to have been controlled via radio, with a range of about 1000 km.
The drones do not technically swarm, though. Instead, the Geran-2 is simply launched in bunches in order to overwhelm defences, particularly in civilian areas.
The incessant buzzing of the propeller-driven Geran-2 drones - dubbed "mopeds" and "lawnmowers" by combatants - can induce terror for anyone under its flight path because no one on the ground knows exactly when or where the weapon will strike.
Unlike other drones that return to base, the Geran-2 are destroyed in an attack.
Samuel Bendett, a Russian military weapons expert at the US Centre for Naval Analyses, said the drones were "simple".
"They don't have very sophisticated electronics," he said.
"They use civilian GPS technologies to navigate the target. That means a robust and capable electronic war system can jam and interfere with this signal."
A man dives for shelter on the pavement during a drone attack in Kyiv on Monday. The drones induce terror because no one on the ground knows exactly when or where the weapon will strike. Photo: AFP
How big are they?
In the scheme of things, the Geran-2 drones are not huge- but they are also a whole lot bigger than your average drone.
According to the Ukrainian online publication Defence Express, which cites Iranian data, the delta-wing drone is 3.5m long, 2.5m wide and weighs approximately 200kg.
It is powered by a 50-horsepower engine with a top speed of 185 kph.
Where do they get them from?
Ukrainian and US officials say the drones that Russia has been deploying are manufactured in Iran.
Ukrainian President Volodymyr Zelensky, citing Ukrainian intelligence services, alleged Russia ordered 2400 drones from Iran.
A boy holds at a protest outside the Iranian embassy in Warsaw on Monday. Several hundred people protested the supply of loitering Shahed drones to Russia. Photo: AFP/ NurPhoto - STR Jaap Arriens
Ukraine military intelligence chief Kyrylo Budanov said that Iran provided Russia with a first batch of 1750 drones and Moscow placed orders for more.
Foreign Minister of Ukraine Dmytro Kuleba called for European Union sanctions on Iran for providing drones to Russia, and both he and Zelensky reiterated Ukraine's need for air defences and weaponry.
Iran had denied supplying the drones to Moscow, although its Revolutionary Guard chief had boasted of providing arms to the world's top powers, without elaborating.
Washington said Iran's denial was a lie.
The Kremlin on Tuesday denied its forces had used Iranian drones to attack Ukraine.
Speaking from the Pentagon on Tuesday, State Department principal deputy spokesperson Vedant Patel said potential Iranian transfers with Russia were "deeply concerning".
"Russia becoming more reliant on a country like Iran, a country known for its destabilising actions in the region and across the world, should be deeply concerning to the world," he said.
Why is Russia using them?
Also known as "the poor man's cruise missile," the drone is only a tiny fraction of the cost of a full-size missile at only $US20,000 apiece.
Firefighters work on a destroyed building after a drone attack in Kyiv on Monday. Photo: AFP / Yasuyoshi Chiba
In comparison, Russia's Kalibr cruise missiles, which there had been widespread use of in the eight months of war, cost the Russian military about $US1 million each.
Because they are cheap and plentiful, Russia had the ability to flood Ukraine with the Geran-2 without risking the lives of pilots or putting sophisticated aircraft at risk.
It could then save its limited stock of expensive long-range precision missiles.
Expert Samuel Bendett said Russia turned to the Geran-2 to launch in bunches to overwhelm defences, particularly in civilian areas.
"Russia entered the war with a significant stock, but that has since been depleted," he said.
"In order to stalemate Ukrainians to stop their advances, Russians needed something that would be able to cause a significant amount of damage."
On Wednesday, Zelensky condemned Russia for sourcing weapons from Iran.
"Let us bear in mind that the very fact that Russia has sought help from Iran is an admission by the Kremlin that it is bankrupt in military and political terms," he said.
How many does Russia have?
The military downside to the "kamikaze" drones is that they can only be used once.
In Monday's attack on the Ukrainian capital of Kyiv, the city's mayor Vitali Klitschko said 28 drones made up waves of successive attacks.
So while Zelensky alleged Russia ordered 2400 drones from Iran, it was not known exactly how many had been used or what Russia's futures plans are now.
Bendett said it was known that Russia "may be acquiring an even larger tranche of these loiter ammunitions in the coming weeks and months."
He said it indicated Russia was prepared to use the drone technologies long-term heading into the winter to cause "as much damage as possible to the Ukrainian civil energy infrastructure".
-ABC