Four soldiers deployed to Lake Chad were killed when a mine set by jihadists blew up their boat, Chadian sources said on Wednesday.
The incident happened on Tuesday in the vast, marshy lakelands, where Chadian forces are battling a years-long jihadist insurgency, they said.
"Boko Haram placed an improvised device in the water, which exploded when their canoe passed by, killing four soldiers and wounding about 20 others," an army officer told AFP, speaking on condition of anonymity.
Dimoya Souapebe, the prefect (state representative) for the region confirmed the toll, and said the canoe, also called a pirogue, had been transporting troops between Ngouboua and Litri.
Chad, along with Niger and Cameroon, is struggling with a jihadist campaign that Boko Haram launched in northeastern Nigeria in 2009 and then took into the wider Lake Chad region.
More than 36,000 people, most of them in Nigeria, have been killed and some three million have fled their homes, according to UN figures.
The lake's marshland, dotted with islands, is used as a refuge by the jihadists.
Chadian officials typically make no distinction between Boko Haram and a dissident group, the Islamic State West Africa Province (ISWAP), in their reference to the jihadists.
Six Chadian soldiers were killed in an ambush in the Lake Chad region on October 20.