A group that monitors extremist organizations says the Islamic State group has posted what is thought to be the first video from IS-affiliated fighters in Somalia.

The video posted online Monday calls on supporters to "hunt down" what it calls nonbelievers and attack churches and markets.

The SITE Intelligence Group says the video urges supporters to take advantage of people's "drunkenness" over the holiday season to attack.

The United States last month launched its first drone strikes against Islamic State group-affiliated fighters in Somalia. The Horn of Africa nation has a small but growing presence of the fighters, many of them defectors from the al-Qaida-linked al-Shabab extremist group.

The fighters are based in northern Somalia's rural Puntland. Experts warn their numbers could grow as IS fighters flee Syria and Iraq.