Raipur: Twelve policemen and a civilian were killed and six others injured after 150 heavily armed Maoist guerrillas ambushed a 41-member police force in Chhattisgarh, government officials said on Monday.

The attack on the District Force search convoy in Dhamtari district's hillside village, Risgaon, took place late on Sunday.

"The heavily armed rebels first triggered multiple blasts and then opened indiscriminate fire from hilltops on jawans.

"Ten constables, one hawaldar, one special police officer (SPO) and a civilian, who was the driver of one of the vehicles, were killed," Girdhari Nayak, additional director general of police, told IANS.

The incident took place 130km from here.

"It's the first attack of insurgents in Dhamtari district. The jawans belonging to Kanker DF were travelling in three vehicles," said Pawan Deo, deputy inspector-general (Maoist operations) at the police headquarters.

A helicopter sent by the state government yesterday morning brought back three seriously injured policemen who have been admitted to the Ramkrishna Care Hospital here.

The search squad was sent to the area after intelligence inputs suggested that dozens of Maoists were to meet there. The information proved to be a trap.