Armed PLFI ultras arrived at the site near Karo river on Tapkara-Rania Road under Tapkarao outpost late last night, beat up some labourers and torched the equipment.
Two tractors, a dumper, an earth moving machine, two generator sets and a jointer machine used by a Bengaluru-based company hired by IOC were set ablaze, police said.
Security forces have launched a search operation to track down the ultras.
Later, Director General of Police D K Pandey, DIG (Ranchi) R K Dhan and district Superintendent of Police Ashwini Kumar Sinha went to the spot for inspection.
The DGP directed the police to provide security to ensure completion of the work as well as other development works in naxal-affected areas after he had a meeting with the District Armed Police, CRPF and Intelligence officials.
Pandey said that naxal and extremist activities would be wiped out from the state in 2017.