At least four Burkinabe soldiers were killed in a jihadist attack on Monday in the restive north of the country, security sources told AFP.
Jihadists ambushed the troops a few kilometres from the Niger border in Yagha province, a security source told AFP, saying four were killed and four others were still missing.
Another security source confirmed the attack, adding that authorities were now trying to find the missing soldiers and track down the attackers.
"Armed groups are moving from one side of the border to the other, carrying out attacks in both countries," the security source said.
Both sources said the attack took place in a village called Kankanfogouol.
Burkina Faso is involved in a regional effort to battle an Islamist insurgency, along with neighbouring Mali and Niger, Mauritania and Chad.
However, Burkina Faso's security forces have been unable to stem the violence despite help from France, which has roughly 5,000 troops in the region.
According to UN figures, jihadist attacks in Burkina Faso, Mali and Niger left nearly 4,000 people dead last year. Some 800,000 people have been displaced since 2015.