MOGADISHU - Clashes erupted early Thursday between rival insurgent groups in the southern Somalia port of Kismayo, witnesses said.
The Shebab and the Hez al-Islam battled for control of the port and hundreds of families fled Kismayo, witnesses said.
The two groups are normally allies in the insurgency against Somalia's transitional government.
The two factions had agreed to share power in Kismayo, with each governing for six months alternatively, but clan politics seeped in and the rotation failed when the Shebab refused to relinquish the administration.
Firmly under rebel control for more than year, Kismayo had been relatively quiet until Thursday.
"We were attacked by our brothers with no reason," local Hezb al-Islam spokesman Sheikh Ismail Haji Adow told reporters.
"They (the Shebab) launched their offensive on several fronts very early this morning. The fighting is very intense but we are holding up," he said.
Kismayo had attracted many Somalis who had fled the capital Mogadishu, which has been plagued by almost uninterrupted violence over the past three years.
It was not immediately clear what impact the rupture in the country's main rebel alliance would have on the broad military offensive the two insurgent groups launched against the government on May 7.
For almost five months, the two armed factions have led a bruising campaign to oust government fighters from key towns and topple cleric President Sharif Sheikh Ahmed.
The Shebab has been taking extreme stances since it broke away from the Islamic Courts Union (ICU), who ruled much of Somalia with relative peace and prosperity until the Ethiopian invasion late 2006.
After the Ethiopian troops ousted the ICU, Somalia plunged into unprecedented chaos, where warlords and pirates have returned to the scene.
The US-backed Ethiopian troops in Somalia had resorted to throat-slitting executions and gruesome methods that include rape and torture.
As a result, the Shebab has become increasingly radicalised and has spearheaded an insurgency against the Somali government, whose president today is a former ICU leader.
Despite the Ethiopian withdrawal, it is unlikely that Somalis would soon be returning to the period of calm and security enjoyed under ICU rule.
The US and its allies in the region, who were not happy with the then relatively popular and stable ICU, will likely to face a non-negotiating force when dealing with the Shebab.
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