Two suicide attackers set off bombs outside the African Union's main peacekeeping base in Somalia's capital Mogadishu near the airport today, police said.

The first detonated a car bomb and the second tried to storm the base on foot, but was shot and exploded at the gate, officers added.

"AU forces sealed the area. There were many Somalis outside the gate and there were AU forces at the gate - we have not yet confirmed the casualty figure," police officer Major Nur Osman told Reuters.

There was no immediate claim of responsibility, though the Islamist al Shabaab militant group has launched a string of assaults in the capital and beyond in its campaign to topple the Western-backed government.