The Kenyan Defense Force said in a Twitter message the attack occurred as militants met at a camp in the western Gedo region of Somalia near the Kenyan border, CNN reported.
Preliminary reports indicated "key commanders" were among those killed. Dozens of other militants were said to have fled with multiple injuries.
The raid destroyed vehicles and equipment.
The al-Qaida-linked al-Shabaab organization, which controls part of Somalia, was responsible for a September attack on a Nairobi shopping mall that resulted in more than 70 deaths.