N'Djamena (AFP) - Six people, including two soldiers, died in an overnight Boko Haram attacks near Lake Chad, security and army sources said on Saturday, saying Chadian troops had killed 17 assailants in a counter-offensive.

Three forestry officials and a customs officer and two soldiers were killed in attacks on Moussarom and Ngueleya located in the Lake Chad region, south of Baga Sola, a security source told AFP.

"The attackers were later repelled," the source said.

Chadian army spokesman Colonel Azam said "17 Boko Haram members have been killed" although he put the civilian death toll at three instead of four.

The last Boko Haram attack on the Chadian side of the lake happened on July 22 in which 18 people were killed in a village south of Daboua near the border with Niger.

Boko Haram's Islamist insurgency has devastated the region since it took up arms in 2009 in Nigeria, leaving at least 20,000 people dead, displacing more than two million others and triggering a humanitarian crisis.

Chad, Cameroon and Niger have all joined the military effort by Nigeria to crush Boko Haram. Chad has seen a recent increase in attacks by the group.