By Feisal Omar and Abdi Sheikh

MOGADISHU (Reuters) - A group loyal to Islamic State seized the small port town of Qandala in Somalia's semi-autonomous Puntland region on Wednesday, the first town it has taken since emerging a year ago, officials said.

The group, which refers to itself simply as Islamic State, is a rival to the larger al Shabaab force, which is linked to Islamic State's rival al Qaeda and once controlled much of Somalia.

"Our soldiers were few and so could not fight longer," district commissioner Jamac Mohamed Khuurshe said. African peacekeepers are not deployed in Puntland, which lies at the eastern tip of the Horn of Africa.

Soldiers and many residents fled and the militants cut off Qandala's communications, Khuurshe said.

Earlier on Wednesday, al Shabaab seized a town in southern Somalia after African and Somali government troops withdrew, part of an ongoing back and forth in the region.

Islamic State has been gathering recruits in Puntland, although experts say the scale of its force is unclear and it remains a small player compared to al Shabaab.

Before Qandala's phone lines were cut off, fisherman Abdirahman Hussein told Reuters: "We just saw Daesh (Islamic State) with their black banner as we were fishing. They said to us: 'Don't panic, we will rule you according to the Islamic sharia (law)'."

Major Saiid Ali, a Puntland police officer, said the group had previously entered two small villages before retreating to hideouts in the Puntland hills, but had never before seized a town.

The Puntland Islamist group first announced its alignment to Islamic State a year ago in a statement on YouTube.

The group is led by Abdiqadir Mumin, a former al Shabaab commander, a sign that some al Shabaab fighters see al Qaeda as a spent force and have been inspired by Islamic State's campaign in Iraq and Syria.

Several groups beyond Islamic State's Middle East heartland have made similar declarations of allegiance, although experts say these links are unlikely to go much beyond ideological sympathies.

Al Shabaab has yet to make any comment on the Puntland group.

Separately, al Shabaab said it was behind the killing of a 60-year-old colonel, Siyad Mohamed, in Mogadishu late on Wednesday, following the assassination of an intelligence officer in the capital on Monday.

Al Shabaab's seizure of Tiyeeglow in southern Somalia on Wednesday gave it back control of an area over which it has long fought with the African Union's AMISOM force and Somali soldiers.

Ethiopian government spokesman Getachew Reda said the Ethiopian troops that withdrew were not part of Ethiopia's AMISOM contingent, and that any redeployment was done in consultation with Somali troops.

(Additional reporting by Abdiqani Hassan in Puntland, Aaron Maasho in Addis Ababa and Feisal Omar in Mogadishu; Writing by Edmund Blair and George Obulutsa; Editing by Tom Heneghan and Kevin Liffey)