|AU troops killed in Somalia clashes|
Fighting between peacekeepers and al-Shabab leaves 53 soldiers dead and scores wounded, the vast majority from Burundi.
The fighting started two weeks ago in the Horn of African nation which has had no central government for two decades and is struggling to rein in the group, the former military wing of the deposed Islamic Court Union.
Two Nairobi-based diplomats, speaking on condition of anonymity, said at least 43 Burundian and 10 Ugandan troops have been killed since February 18, citing information from people involved in the operation.
The AU force, known as AMISOM, has publicly confirmed only a handful of deaths since the fighting broke out.
The Associated Press news agency said on Saturday that the AU appeared to be trying to conceal losses due to political considerations in Burundi, one of two nations providing the bulk of the forces that are fighting alongside Somali troops.
An AU spokesman in neighbouring Kenya's capital, Nairobi, did not answer calls on Friday and Burundi's government spokesman was unavailable for comment.
Military officers in Burundi's capital, Bujumbura, confirmed the death of the 43 Burundi soldiers, adding that 110 others were wounded.
"In reality, 43 soldiers of the Burundi contingent ... have been killed, another four are missing and 110 were wounded during the last joint offensive ... in Mogadishu," a senior officer who declined to be named due to the sensivity of the issue said.
"The majority of these soldiers were killed on the first day of the offensive. They came upon many insurgents at a major target located near the former defence ministry which we conquered."
The officer added: "The troops' morale is good despite these losses which are the worst since we have been deployed in Somalia, because we achieved our goals."
Meanwhile, an AU commander said on Saturday that his forces had captured a key position from al-Shabab in the capital Mogadishu.
Major-General Nathan Mugisha said the soldiers had captured the former ministry of defence building in the north of the city, gaining control of a major al-Shabab base.
"By taking these positions we have effectively reduced their freedom of manoeuvre in that sector," Mugisha told a news conference in Nairobi.
"This peace in Mogadishu comes at a price, and this burden has fallen heavily on AMISOM and government forces."
Earlier, al-Shabab fighters were forced to abandon their positions in Belet Hawo, a town which borders Kenya, said Sharif Abdiwahid Sharif Aden, a spokesman for pro-government armed forces.
The latest offensive aims to break al-Shabab's hold on large swathes of the country's south and central regions.
The group - which has instituted a Taliban-style system of rule, with strict edicts enforced by its own courts and public executions - has boxed in the government to just a few city blocks of Mogadishu.
The transitional government has been promising a full-scale war against al-Shabab for years, but co-ordination among its poorly trained, seldom-paid government forces has delayed that push.
A report last month by the think-tank International Crisis Group described the government as being on "life support".