The incident occurred around 4 pm near Murdanda camp of the CRPF under Awapalli police station, when its 168th battalion was out on "area domination" operation, Bijapur Superintendent of Police Mohit Garg told PTI.
When the MPV carrying six personnel was around one km away from the camp, ultras triggered a powerful land mine blast, he said.
"Four paramilitary personnel were killed and two others were injured in the blast," he said.
Reinforcement was rushed to the spot immediately and the injured personnel were being evacuated, the official said, adding they were retrieving the bodies from the site.
The attack took place on a day when Chief Minister Raman Singh launched the ruling BJP's campaign for the first phase of polls on November 12 in neighbouring Sukma district.
The first phase of election will cover 18 constituencies in eight Naxal-affected districts - Bastar, Kanker, Sukma, Bijapur, Dantewada, Narayanpur, Kondagaon and Rajnandgaon.
Naxals had recently put up posters in parts of Bastar region calling for boycott of the polls.