Fighters from Hezb al-Islam joined the ranks of Al Qaeda-linked Shehab militants battling against African Union-backed forces of the fragile transitional government, according to witness reports.
"We have decided to rejoin the Shebab and dissolve Hezb al-Islam. I can tell you from today (Sunday) our group, including the highest commanders, will become members of the Shehab," said Mohamed Osman Arus, a Hezb al-Islam spokesman.
The spokesman said the agreement was reached after talks between leaders of the groups, following several weeks of tension which included the Shehab forcibly taking a town held by Hezb al-Islam.
Islamist fighters control much of central and southern Somalia. The transitional government says it controls more than half of the capital Mogadishu, but swathes remain no-go areas controlled by the Shehab.
No leaders of the Shehab could be reached to confirm the agreement with Hezb al-Islam.