of landThe Russian army has left thousands of unexploded mines in territories that the Ukrainian army recently liberated, all of which may take years to demine, President Volodymyr Zelensky said Thursday.Zelensky added that the unexploded mines and munitions were found in critical infrastructure facilities as well as civilian areas, including houses, roads, power lines and enterprise buildings."In particular, thanks to such aid, we have already purchased the first most effective demining machine - Armtrac 400 which is currently operating in the Kharkiv region."Zelensky's address comes as Ukraine's military announced Thursday that it has retaken territory in Kherson Oblast after Russia ordered the withdrawal of its troops from parts of the region.Over the past two days, Ukrainian forces have successfully recaptured and liberated 24 settlements in the Kherson region."