Speaking to reporters, Pillai said, "Our resolve against the Naxals strengthened further. We will give them a firmer reply."
"Initial reports suggest that the Naxals used pressure bombs," Pillai said.
The Home Secretary further said, "One rescue helicopter too came under Naxal fire, but we have managed to bring back seven personnel injured in the attack."
"There was some failure", Pillai said adding "we shouldn't have lost so many lives."
"Our hearts go out to the families of those who have been killed," he added.
At least 74 CRPF were killed in an ambush in the thick Mukrana forests of Chhattisgarh's Dantewada district.
According to reports, the dead include a Deputy and an Assistant Commandant, and a head constable of the district police force.
In view of the incident, a high level National Security Council meet was called at the PM"s residence to take stock of the situation and to decide on the future course of action.
The meeting is being attended by Home minister P Chidambaram, Finance Minister Pranab Mukherjee, Defence Minister AK Antony, National Security Advisor Shiv Shanker Menon, GK Pillai and the chief of India"s premier intelligence agency RAW.