Kyiv: Ukraine's 57th Motorized Brigade released drone footage which it said shows forests in the Kharkiv region covered with fibre-optic cables left behind by Russian drones.

The location and date of when the video was filmed could not be verified. However, the brigade said the video was filmed in a forest near Vovchansk, an embattled north-eastern town. Ukraine's DeepState military blog, which uses open-source reports to track the positions of both armies, estimates that most of Vovchansk is held by Russian troops, with some neighbourhoods in the town's south marked as 'infiltration area.'

Fibre-optic drones have become increasingly common on the battlefield because they are immune to electronic jamming, with cables stretching for kilometres behind them as they fly.

Researchers say the cables are becoming part of the natural environment, with birds even using the material to build nests near the front line.

The brigade described the discarded cables as a long-term environmental problem in a region heavily affected by the war.