The areas around the presidential palace and police headquarters in N'Djamena - one of the targets of the bombers - were sealed off, checkpoints were set up across the city and vehicles with smoked glass windows banned from the roads, AFP journalists reported.
Chad has been on the front line of a regional fight against the Nigerian Islamist group, but yesterday's attack marked the first of its kind in the capital of the north- central African country.
It said four "terrorists" were also killed in the blasts, but did not give details.
Although Boko Haram has yet to claim responsibility for the suicide bombings, which also targeted a police academy, both Chad and France accused the militants of being behind the "barbaric attack".
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Abubakar Shekau, the leader of the fundamentalist movement, has threatened several times to attack Chad and other countries that have joined forces to fight Boko Haram.
President Mahamadou Issoufou of neighbouring Niger firmly condemned "these acts of unspeakable cruelty" in a statement read late Monday on state television.
Issoufou urged the international community to back member states of the Lake Chad Basin Commission in a joint struggle against Boko Haram, which on April 25 killed 74 people, including 28 civilians, in a raid inside Niger.
That attack against a military outpost on Lake Chad, where regional borders converge, also left 32 people missing, making it the bloodiest assault against Niger since it entered the fray against the militants.
Months before that decision, troops from Chad and Niger began a ground and air offensive on Nigerian soil and took back big swathes of territory from the Islamists, whose name loosely translates as "Western education is forbidden".
The movement is believed still to be holding more than 200 schoolgirls abducted in a raid on a state school at Chibok in northeastern Borno State in April 2014.