In a major setback to Maoists,the Orissa police on Tuesday recovered a massive arms and ammunition dump including 15 landmines,17 detonators and 6 pressure bombs from the deep jungles of Rayagada district. Meanwhile,in Orissas Sambalpur district,a hardcore Maoist from Jharkhand involved in arms training to Maoists in Saranda forest and his three associates were arrested on Monday night. Sambalpur SP Nikhil Kanodia said Ranbir Jharna alias Mangala,was arrested when he was in Sambalpur to buy materials for Maoist activities. Jharna,along with his accomplices,Mangalu Munda,Basant Harenz and Durga Topno,was staying in a rented house at Deheripalli locality.