Gunmen are attacking the army's headquarters in the capital of Burkina Faso as well as the downtown area and France's embassy.
The French ambassador says an explosion in the city was a terrorist attack.
It's not clear who was behind the violence but Burkina Faso and other West African countries have been targeted by jihadist groups linked to al-Qaeda and Islamic State in the past few years.
A local news station showed pictures of black smoke coming from a building in central Ouagadougou and a Reuters correspondent found that most people had fled the streets.
"Attack under way at the French Embassy and French Institute. Stay hidden where you are," the embassy said in a statement posted on its Facebook site.
A French official in Paris confirmed that an assault against the embassy, as well as against the Burkina Faso army headquarters.
An explosion rocked the army headquarters and then gunfire rang out in the vicinity. A witness said masked gunmen with backpacks had attacked the army headquarters shortly before the explosion.
Islamist militants have gained a stronger foothold in Africa's vast Sahel region in the last few years, launching attacks in Mali, Burkina Faso, Ivory Coast and Niger.
Suspected jihadists killed at least 18 people last August during a raid on a restaurant in Ouagadougou, and militants have targeted Burkinabe security forces along its remote northern border region with Mali.
Al Qaeda in the Islamic Maghreb (AQIM) claimed responsibility for an attack on a restaurant and hotel in Ouagadougou in January 2016 in which 30 people were killed.
