Crowds of Somali residents look as the bodies of African Union soldiers who were killed during clashes between AU peacekeeping forces and Islamic insurgents are displayed in southern Mogadishu's Daynile neighborhood. (AP Photo/ Farah Abdi Warsameh)

NAIROBI, Kenya (AP) — More than 50 African Union  peacekeepers have died in fighting in Somalia since a major offensive against Islamist militants began two weeks ago, officials told The Associated Press on Friday.
The death toll is far higher than any publicly acknowledged casualty figures for the AU, which appears to be trying to keep the extent of its losses under wraps due to political considerations in Burundi, one of two nations providing the bulk of the forces that are fighting alongside Somali troops.
The offensive aims to break Islamists' lock on large swaths of the country's south and central regions. Al-Shabab, a Somali militant group with links to al-Qaida, has boxed in the government to just a few city blocks of the seaside capital. The group has instituted a Taliban-style system of rule, with strict edicts enforced by their own courts and public executions.
The government has been promising a full-scale war against militants for years, but coordination among its poorly trained, seldom-paid government forces has delayed that push.
The AU force, known as AMISOM, has publicly confirmed only a handful of deaths since heavy fighting broke started Feb. 19. An AU spokesman in Nairobi did not answer calls Friday. Burundi's government spokesman was unavailable for comment.
Wafula Wamunyinyi, the second-highest ranking official on the AU's commission for Somalia, declined to discuss casualty figures when reached Friday.
"I don't have that information where I am now," he said.
Two Nairobi-based diplomats said at least 43 Burundian and 10 Ugandan troops have been killed since Feb. 18, citing information from people involved in the operation. The two spoke on condition of anonymity because they were not authorized to speak to the press.
In addition, a Burundian soldier has been captured alive by militants, and his image and a recorded statement have been circulating on websites used by al-Shabab, Somalia's most dangerous insurgent group.
AMISOM says hundreds of militants from al-Shabab have been killed in the offensive. AMISOM officials say peacekeepers have taken back insurgent-controlled areas of Mogadishu, the capital. The AU says it controls up to 60 percent of the city.
There are around 8,000 AU forces in Mogadishu, with another 4,000 due to begin arriving over the next few months. Almost all are Ugandan or Burundian. They support the country's weak U.N.-backed government against al-Shabab.
Few officials seem willing to acknowledge the heavy casualties AMISOM troops have suffered. But a statement from France's Ministry of Foreign and European Affairs on Tuesday said that France evacuated 13 AMISOM troops by military aircraft to neighboring Djibouti, where the French have a base, for medical care.
Since the offensive began, AMISOM troops have taken three key militant positions, including the former defense ministry that overlooks Bakara market, an insurgent stronghold. If the AU is able to deny al-Shabab access to the market, it might be able to deny the insurgency a key revenue stream — collecting taxes from traders.
Troops also uncovered a mile-long tunnel network that militants were using to move fighters and ammunition close to AU positions in government-held areas. Fighting has been fierce, often building-to-building. During a prior visit to Mogadishu, AU soldiers showed AP how they were able to move from house to abandoned house by punching holes in the walls between them.
The AU troops fight with no air support, little body armor and armored vehicles that are vulnerable to attack by rocket-propelled grenades.
The fighting has spread beyond the Somali capital, to the Kenyan and Ethiopian borders. In Somalia's south, fighters secretly recruited from refugee camps in 2009 and trained in Kenya have been pressed into action. A clan-based militia nominally allied with the Somali government, Ahlu Sunnah Wal Jama, is fighting the Islamists in Somalia's southeast.
It remains unclear whether the Somali government and its international backers have any plan to secure and develop territory they gain. The government has long failed to provide services or security to its people and its mandate expires in August.
The corruption and inefficiency has greatly hampered efforts to wrest back control of the country from the Islamists. Unpaid soldiers often sell their arms or ammunition, sometimes even to the other side.
A report last month by the think tank International Crisis Group described the government as being on "life support." It urged the international community to redirect funding and support to regional administrations if the Somali government does not make significant progress in building alliances and providing better services.
Somalia has not had a functioning government for more than 20 years. Its lawless shores are a haven for pirates and intelligence agencies fear the failed state is also a training ground for international terrorists. Last July, the Somali insurgency launched its first foreign attack, multiple suicide bombings in Uganda that killed 76.
Medical authorities say the most recent round of fighting has killed more than 100 Somali civilians.