A police commander and seven civilians have been killed in Mogadishu, the Somali capital, police officials say.

Government forces attacked opposition strongholds in the city, triggering a battle with fighters from the al-Shabab movement on Wednesday, they said.

Colonel Abdulahi Hassan Barise, a police spokesman, confirmed that Colonel Ali Said was the police commander among the people killed in crossfire during the attacks.

Residents said they watched Islamist fighters wearing headscarves and ammunition belts arriving from the outskirts of the capital to join the battle.

Asha Moalim, a Mogadishu resident, said: "This is the strongest fighting we have seen in recent months."

A surge of violence in Somalia's capital since last month has killed about 200 people as Somali fighters battle the interim government and its allies.

The fighters want to topple the Western-backed government. Somalia has had no effective central government for nearly two decades amid widespread tribal power struggles.