"The two women suicide bombers and two civilians died in the blast," the source told AFP on condition of anonymity, adding that "14 others were injured" in the attack blamed on Nigeria's Boko Haram group on Ngouboua village near the Nigerian border.
The village has suffered repeated attacks by Boko Haram jihadists since they first launched operations in Chad in February.
Suicide bombings -- many by women and girls -- are fast becoming Boko Haram's preferred method of inflicting civilian casualties.
Since the start of the year, the Chadian army has been on the frontline of a regional military operation against Boko Haram whose attacks have spread from northeast Nigeria, its traditional stronghold, to the neighbouring countries of Chad, Niger and Cameroon.
Boko Haram, which is affiliated with the Islamic State group operating in Syria and Iraq, has been hit hard by the offensive, losing territory, but has launched attacks and bombings in response.