Four village Special Police Officers were killed and three others injured when around 300 heavily armed Maoists attacked a relief camp in Dantewada district of Chhattisgarh on Saturday, police said.

"Around 300 armed Naxalites [Images] attacked the Injeram relief camp, 540 km from Raipur, and opened indiscriminate fire, killing four village SPOs and injuring three others in the wee hours on Saturday," Dantewada police sources said.

Nagaland Armed Police personnel, who were camping in the same locality, retaliated and the exchange of fire with the ultras continued for over an hour in Injeram, the sources said.

After Naxalites increased their violent activities in June last year, about 50,000 people had deserted their villages and took shelter in government-run relief camps in Dantewada district and about 6000 villagers are staying in such camps at Injeram, the sources said.

The government had recruited some villagers as SPOs to provide them security.

In a separate incident on Friday, the Maoists abducted at least two villagers from their village Akhirguda in Dantewada district, police said.

"When the villagers from Akhirguda had gone from the Injeram relief camp to their village, they were abducted by the Maoists on gun point," the sources said, adding that the villagers have lodged a First Information Report in connection with the incident.

Recently, the Maoists had abducted 52 villagers of Manikonta in Dantewada district and killed 15 of them, releasing the rest after threatening them not to participate in anti-Naxal activities.