The skirmish took place in the forest of Tumdiwal region under Mardapal police station limits in which the two STF personnel were killed, Special Director General of Police (anti-Naxal operations) D M Awasthi told PTI.
A joint team of STF and district force had launched the operation towards interior forest of Mardapal, around 350 kms from the state capital Raipur.
When the security personnel reached the forest of Tumdiwal today, they came under heavy firing from a group of ultras leading to the gun battle between the two sides.
Reinforcement was rushed to the spot and the bodies of the personnel are being evacuated from the forest, he said.
Further details were awaited as the exchange of fire was still reported to be on, he added.