At least 50 African Union soldiers are believed to have been killed and another 50 are missing after Shebab militants overran a military camp in southern Somalia on Tuesday, according to Western military officials.

The attack on the camp in Janale, 80 kilometres (50 miles) southwest of Mogadishu in the Lower Shabelle region and manned by Ugandan troops, now ranks as one of the deadliest yet against AMISOM troops.

"It is assessed that at least 50 AMISOM troops died," said a briefing note sent to diplomats by Western military officials and seen by AFP. It said that in total around 100 soldiers were "unaccounted for" after the attack.