The encounter took place when Kumar on getting information that 'Chandanji's dasta', firing squad of the Maoist leader was at a place on Khunti-Ranchi road headed the search operation.
When the police approached the area, they came under fire and the SSP's driver was killed, Jharkhand Director General of Police D K Pandey told PTI.
"Ranchi SSP Prabhat Kumar suffered bullet injury on his right shoulder. He has been admitted to a hospital and is out of danger," Pandey told PTI.
Two Maoists were also injured in the encounter, he said.
Union Home Minister Rajnath Singh spoke to the SSP and Chief Minister Raghubar Das, official sources said.
Das has asked the officials to ensure that the injured police officer and his body guard gets proper treatment, the sources added.