A statement from US Africa Command on Tuesday said the airstrike was carried out Monday near Jilib in Middle Juba region.
The US has carried out a growing number of drone strikes in the Horn of Africa nation in coordination with Somalia's government. Most are against al-Shabab but a small number have targeted Islamic State group-affiliated fighters in the Puntland region in the north.
Monday's strike is the sixth air attack against Islamic extremist fighters so far this year. The US military reported two strikes last week.