MOGADISHU (Reuters) - A Somali general was shot in the head and killed in the capital Mogadishu on Thursday and a colonel who was his deputy has been arrested for the murder, senior army sources said.

The killing of Marine general Saiid Aden Yusuf in what was apparently an internal dispute is a fresh sign of problems facing the army as it battles an insurgency by Islamist militant group al Shabaab with the help of African Union peacekeepers.

“Our marine general was killed by his deputy at Mogadishu seaport today. The murderer was seized. It was unfortunate and unexpected. An investigation goes on,” marine officer Ahmed Ali told Reuters.

Mogadishu resident Nur Mohamed told Reuters the colonel fired several shots from his pistol and hit the general in the head.

“I was chatting with the general shortly before he was killed .... I heard the gunshots and when I ran to the scene I was shocked to see the general lying on the ground, bleeding,” he said, adding that Yusuf died on the scene from bullet wounds.

Marine officer Ahmed Ali said the colonel was arrested.

Al Shabaab is fighting to oust the government and establish its own rule based on its strict interpretation of Islam’s sharia law.

The group has been pushed out of most of its urban strongholds but it is able to mount deadly attacks in Mogadishu and elsewhere.

Somalia has faced violence and lacked a strong central government since President Mohamed Siad Barre was overthrown in 1991.