Seven police personnel were killed after Naxals blew up their vehicle in Chhattisgarh's Dantewada district on Sunday, police said.
The attack took place on a day when Union Home Minister Rajanth Singh was scheduled to arrive in the state.
Naxals carried out a land mine blast around 12 noon when a joint team of the Chhattisgarh Armed Force and the District Force was patrolling the Cholnar-Kirandul road to provide security to trucks carrying construction material for road works between Kirandul and Palnar villages, a senior police official said.
The intensity of the blast, which took place near a culvert, was strong enough to toss the police vehicle in a roadside ditch, he said.
Five personnel died on the spot and two were rushed to the National Mineral Development Corporation's hospital at Kirandul. One of them died during treatment at the hospital and another was airlifted to Raipur, where he died, the official said.
Those killed from the DF were identified as Head Constable Ramkumar Yadav, Constable Tikeshwar Dhruv and Assistant Constable Shalik Ram Sinha, he said.
The official said that from the CAF's 16th battalion, Head Constable Vikram Yadav and constables Rajesh Kumar Singh and Ravinath Patel were killed in the attack.
CAF Constable Arjun Rajbhar, who was airlifted to state capital Raipur, died during treatment, he said.
Naxals looted six automatic weapons -- two AK-47s and as many INSAS and self loading rifles -- of the deceased personnel, he said.
Police sources believe that the attack was in retaliation to the recent encounters in Gadchiroli (Maharashtra), Malkangiri (Odisha) and Bijapur (Chhattisgarh), where Maoists suffered major casualties.
Combing operations have been intensified in the area following the attack, the official said.
Condemning the attack, Chief Minister Raman Singh termed it "cowardly" and said it exposed the rebels' anti-people and anti-development mindset.
"Our police personnel have sacrificed their lives while guarding a road construction site. Their sacrifice will always be remembered," he said.
"This proves that Naxalites do not want villagers and tribal people of this district to have access to even basic facilities such as roads. Incidents like these cannot dampen the courage and determination of our police force and officials, employees and labourers associated with road construction," Singh said.
"We are committed to provide all-weather transportation facility by developing a network of roads in the entire Bastar division, including Dantewada," the chief minister said.
Earlier, Naxals had carried out a land mine blast in Chhattisgarh's Sukma district on March 13 in which nine CRPF personnel were killed.
Rajanth Singh is scheduled to arrive in Surguja district this evening to attend the passing out parade of the CRPF's Bastariya battalion on Monday.