President Barack Obama left the US for Kenya on Thursday in a trip that will also include a stop in the Ethiopian capital and a visit to the home of the African Union.

The landmark trip to Obama's ancestral homeland of Kenya, where his father was born, is his first as president and is also the first time a sitting US leader will visit Ethiopia and the AU's headquarters.

The first African-American US president is expected to address regional security issues, and also touch on matters relating to democracy, poverty and human rights in the region.