NAIROBI, Kenya — Kenya's prime minister underwent a procedure to relieve pressure building on the outside of his brain, and doctors said Tuesday he was in stable condition.

Prime Minister Raila Odinga, 65, will remain in the hospital the next five days, said Dr. Oluoch Olunya, a neurosurgeon.

"I would like to assure the country that he is actually well. The headache that he had yesterday has all been cleared," said Olunya.

Odinga was admitted to the hospital late Monday after feeling exhausted. Officials earlier Tuesday had said the prime minister was suffering from fatigue. A statement from the Nairobi Hospital called the procedure doctors carried out late Monday to relieve the pressure "minor."

Odinga became prime minister when he signed a power-sharing deal with President Mwai Kibaki to end violence following Kenya's disputed December 2007 presidential election. More than 1,000 people were killed in the post-election fighting.

Odinga's doctors did not answer questions from reporters and did not specify the exact condition Odinga was suffering from. His doctor said the pressure may have been caused by Odinga banging his head in a vehicles three weeks ago.

One possibility is hydrocephalus, a condition where excessive fluid builds up on the brain. If left untreated, symptoms of the condition include cognitive problems and difficulty walking, according to the website of the Hydrocephalus Association.

Connie Sigei, Odinga's sister-in-law, who visited him in the hospital, said the prime minister was in good condition.

"I brought him boiled maize and he ate it all, drank water and asked for more," she said with a smile on her face as she left the hospital.

The last time Odinga was hospitalized was in 2008 when he underwent an eye operation in Germany.