Dozens of people were killed on Friday in twin attacks on the French embassy in Burkina Faso and the nation's military headquarters, an assault that coincided with a meeting of regional anti-militant forces.
Le Drian says in a written statement that Burkina Faso security forces are mobilized against the assailants, with the support of French security forces, to "reduce the threat".
He further added that the attack might has been planned to target a meeting of the G5 Sahel which was underway in the military headquarters.
French military experts are expected in Ouagadougou to help with the probe, according to a government statement.
In reprisal for Burkina Faso's participation in a regional fight against Islamist militant.
France's defense ministry said French special forces, which have a base in the country, were used to protect French citizens and secure the embassy.
At least 80 people were wounded.
"This is a terrorist attack, linked to a current or another terrorist movement in the Sahel. or to others who want to are destabilise or block our democratic progress", said communication minister Remis Fulgance Dandjinou on Saturday morning.
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Its members "expressed their solidarity with Burkina Faso in its fight against terrorism and stressed the need to intensify regional and worldwide efforts to combat terrorism and violent extremism, which may be conducive to terrorism".
The Paris prosecutor's office said it has opened a preliminary attempted murder investigation into the attack because the embassy was among the targets, a French judicial official said on condition of anonymity because he is not authorised to talk to the media identified.
Authorities have not identified who was responsible for the attacks, CNN reported.
At the same time, the bomb went off near the headquarters of the Burkinabe armed forces and the French cultural centre, about a kilometre from the site of the first attack, other witnesses said.
France has a military presence in Burkina Faso as part of Operation Barkhane, which was launched in 2014 to combat jihadist activity across the Sahel region.
Responsibility was claimed by a group called Al-Qaeda in the Islamic Maghreb (AQIM).
This was the third large-scale attack by extremists on Ouagadougou since January 2016 when 30 people were killed at a popular cafe.
A military barrier is placed along a street leading to Burkina Faso's army headquarters in the capital Ougadougou, Burkina Faso. No one has claimed responsibility for the violence.