Ukrainians warn they're in danger of losing drone arms race - as Russia mastering device that cannot be jammed

Ukrainians say they are in danger of losing the drone arms race with Russia and need more help.

And that is worrying not just for Ukraine, because the drone is becoming the likely weapon of choice in other future conflicts. Sky News has been given exclusive access to a Ukrainian drone factory to watch its start up ingenuity at work.

Ukrainians have turned the drone into their most effective weapon against the invaders. But they are now, we are told, losing the upper hand in the skies over Ukraine.

Drone company General Cherry was started by volunteers at the beginning of the war, making 100 a month, but is now producing 1,000 times that. The company's Andriy Lavrenovych said it is never enough.

"The Russians have a lot of troops, a lot of vehicles and our soldiers every day tell us we need more, we need more weapons, we need better, we need faster, we need higher." The comments echo the words of Ukraine's leader, President Volodymyr Zelenskyy, who told reporters this week "the Russians have increased the number of drones, while due to a lack of funding, we have not yet been able to scale up." The factory's location is a closely-guarded secret, moved often. Russia strikes weapons factories when it can.

In a nondescript office building, we watched drones being assembled and stacked in their thousands. Put together like toys, they are hand assembled and customised.

The quadcopters vary in size, some carry explosives to attack the enemy. Others fly as high as six kilometres to ambush Russian surveillance drones.

A $1,000 (£743) Ukrainian drone can bring down an enemy aircraft worth 300 times as much. Downstairs each drone is tested before it's sent to the front.

Nineteen-year-old Dima - not his real name - used to play with drones at home before it was occupied in Kherson Oblast. Now he works here using his skills to check the drones are fit for battle.

But Russia is catching up. Sinister propaganda, released last month, filmed at one of its vast new drone factories, shows hundreds of Geranium delta wing attack drones lined up ready to be launched at Ukraine.

Russia has refined the technology provided by Iranians to produce faster, more lethal versions of their Shahed drones. They have wreaked havoc and carnage, coming in their hundreds every night and killing scores of civilians.

Ukraine expects 1,000 a night in the months ahead. Russia is using scale and quantity to turn the tables on Ukrainians.

And it is mastering drones controlled by fibre optic thread, trailing in their wake, that cannot be jammed. Read more:Trump sets red line on Ukraine peace deal supportWhat would US-backed security guarantees look like? Oleksandr "Drakar.