sentences:  Much of the AU's opposition comes from an Islamic extremist group named al-Shabaab.To temporarily shore up the government's military base, starting in March 2007, AU soldiers began arriving in Mogadishu as part of a peacekeeping force that was intended by the AU to eventually be 8,000 strong.Eritrea recalled its ambassadors to the African Union on 20 November 2009 after the African Union called on the United Nations Security Council to impose sanctions on them due to their alleged support of Somali Islamists attempting to topple the Transitional Federal Government of Somalia, the internationally recognised government of Somalia which holds Somalia's seat on the African Union.