US President Barack Obama arrived on friday for Kenya, marking his first presidential visit to the homeland of his father. From there, Obama will trace the Great Rift Valley northward to Addis Ababa, becoming the first US president to visit Ethiopia. US and Kenyan officials are fixated on making sure Al-Qaeda's Somali-led affiliate, the Shebab, cannot violently disrupt the US presidential visit this week. President Barack Obama is due to address an international business summit in Nairobi, an event the US embassy itself warned could be "a target for terrorists".