At least 15, mostly civilians have been killed and over 30 others injured in heavy clashes that erupted between Somali militants and government forces backed by African Union troops in the restive capital Mogadishu, witnesses.

The clashes started on late Wednesday in the capital's KM4 and Dabka intersections and Shaqalaha road, where fighters loyal to Somalia's Hizbul Islam carried out surprise attacks on government positions, leading to heavy gun battle.

Eyewitnesses said the fighting killed at least 15 people, mostly civilians and caused the injuries of several other civilians.

Mohammed Osman Arus, Hizbul Islam spokesman confirmed that his forces carried out attacks on government and AU troops, killing several soldiers.

"We carried out attacks on their positions. I saw dead bodies of three AU soldiers with my on eyes," he claimed.

AU troops' spokesman Barigye Bahoku, however, refuted those claims, when reached for comments.

The latest clashes are part of deadly clashes between rebel fighters and government troops backed by AU troops that wrecked the restive seaside capital in recent days.