NEW DELHI — Maoist rebels killed 11 Indian police officers and seized their automatic weapons and ammunition after ambushing a foot patrol on Saturday morning in the eastern state of Chattisgarh, according to a police official.

The rebels first set off explosives and then unleashed a barrage of gunfire that lasted for more than an hour, Jitendra Shukla, the additional superintendent of the Sukma district police, said by phone.

The officers returned fire, he said, but the rebel casualties were unknown.

The attack took place in a remote forested area that is a traditional Maoist rebel stronghold. Its road and communication networks are poor, and three wounded officers were evacuated by helicopter, the same method used to remove the bodies of the dead.

Extra police officers had been deployed to the area on Saturday, which is a market day and brings out larger crowds and more vehicles. The patrol was attacked when it was deployed to check a road for planted explosives, Mr. Shukla said.