Earlier this week, the state IB had intimated district superintendents of police and commandants of armed forces that Maoists are observing "martyrdom week" from November 24-30 in the memory of their slain leader Kishenji during which they may step up their operations.
Kishenji was killed on November 24, 2011 in West Bengal in a special operation conducted by a joint squad of the state police and CRPF.
An advisory by IB also said that ultras will observe the Peoples' Liberation Guerrilla Army week from December 2-8 in honour of slain leaders of the CPI (Maoist), during which again they are likely to intensify and execute attacks on security forces, police stations, camps and also disrupt vehicular movement.
"Even when elaborate inputs were conveyed apprehending that Naxalites may trigger some strikes during this week, such an incident (killing of four CRPF jawans) happened," a senior IB official told PTI requesting anonymity.
The jawans were killed when Naxalites ambushed a road opening party of the security forces in Maoist-infested Bijapur district on Wednesday.
"Now security forces have been told to be more cautious anticipating more such attacks and not to take the situation lightly because of a successful election," he said adding, they were told to stay prepared and strictly follow standard operating procedures (SOPs).
According to the advisory, the IB has called for heightening security around police stations, check posts and camps and conducting area domination within five kilometres radius of these places.
It also asked police jawans and officials to refrain from roaming alone in the region.
Carefully mobilizing on the tip-off about the movement of Naxalites as they may lay ambush in those areas are other precautions given to security forces, according to the IB document.
Twelve constituencies of Bastar division went to polls on November 11 in the first phase of assembly elections amid high security. No major violence was reported on the day in the region except the killing of a CRPF trooper in Dantewada district of south Bastar.
However, on November 12 two Border Security Force personnel and a civilian driver were killed when Naxalites blew up their SUV vehicles near Kerlapal camp while troopers were returning after security deployment for polling in Sukma district.
A record 77 per cent voting was recorded in the just concluded two-phase state assembly elections.