Authorities in Chad say at least five female suicide bombers attacked two sites near the Nigerian border, killing at least 33 locals and Nigerian refugees.
Police immediately linked the attacks in the town of Baga Sola to Boko Haram Islamists.
Police and hospital officials said at least 50 others were wounded in and near the town, located on the shores of Lake Chad.
General Banyaman Cossingar said one of the blasts targeted a local market, while two others ripped through a refugee camp on the outskirts of the town.
Last week, authorities said Boko Haram fighters clashed with Chadian soldiers near Lake Chad. A military source said 11 soldiers and 17 militants were killed.
Chad is a leading contributor to a regional task force set up to fight Boko Haram, whose attacks have spread in recent years from its birthplace in nearby northeastern Nigeria to Chad, Cameroon and Niger.
The militant group has been fighting to establish a strict Islamic state in northern Nigeria since 2009.
The rights group Amnesty International, in a report last month, said Boko Haram had killed at least 1,600 civilians since June, bringing the death toll to 3,500 civilians so far this year.