By Abdi Sheikh and Ibrahim Mohamed

MOGADISHU (Reuters) - Somalia's warring parties pounded each other with artillery in Mogadishu on Friday after an African Union military aircraft defied a rebel ban on planes using the capital's international airport.

Witnesses said at least 15 people were killed.

The bombed-out city's airport had been abandoned since Tuesday after Islamist insurgents from the hardline al Shabaab group vowed to shoot down any aircraft trying to land there.

In another demonstration of their increasing strength, the Islamists also chased away pro-government militia manning roadblocks in the south of the lawless Horn of Africa nation.

On Friday, a plane carrying AU peacekeepers braved the rebel threats and touched down at the Mogadishu airstrip, provoking a barrage of mortar fire from the insurgents.

Government forces and their Ethiopian allies responded with missiles, heavy machine guns and mortar rounds of their own.

An AU spokesman in the city said the aircraft had been carrying troops from Burundi, but that none of them were hurt.

As usual in Somalia, civilians bore the brunt of the fighting. At least four residents died and seven were injured when one shell detonated in the Kilometre 4 area of Mogadishu.

SHELLS KILL CIVILIANS

"A group of local teenagers was sitting playing cards here under a big tree," witness Abdullahi Farah told Reuters. "Now their flesh is scattered everywhere."

Residents said six bodies lay in another area and that a house nearby was hit and burning with three bodies inside.

An official at the city's main Madena Hospital said about 50 wounded civilians had been admitted. Two of them, including a two-year-old child, later died of their injuries.

The Rest @ Reuters Africa