NAIROBI, Kenya (AP) — An alliance of Kenya's main opposition groups has named its presidential candidate to face President Uhuru Kenyatta in the August elections.

The National Super Alliance announced Thursday in a rally attended by thousands of supporters that former Prime Minister Raila Odinga will run for the presidency with former Vice President Kalonzo Musyoka as his running mate.

Odinga said if he is elected he will fight corruption, which observers say is a serious problem in Kenya.

Kenyatta beat Odinga and Kalonzo in 2013 with 50.07 percent of the vote. Kenyatta needed to break the 50 per cent barrier to avoid a run-off with Odinga and he did so by only 4,099 votes out of more than 12.3 million cast. Recent polls have put Kenyatta ahead of Odinga in popularity.