The victims of the blast were all between the ages of 14 and 18, a medical source at the regional hospital in Dapaong who asked not to be named told Reuters.
The explosion occurred in the village of Margba, in the northern Savanes region where Togo declared a state of emergency last month due to rising insecurity.
Local media reported that the young people were returning home at night from celebrations of the Muslim holiday Eid al-Adha when they were killed.
The army did not say whether militant activity was suspected.
"An investigation has been opened to clarify the circumstances of this explosion and identify the perpetrators," said the statement by army chief Dadja Maganawe.
In May, eight soldiers were killed in the same region. The country declared a state of emergency following the attack in what was thought to be the first deadly spillover of Islamist violence from neighboring Burkina Faso.