Kenya Prime Minister Raila Odinga has been admitted to Nairobi Hospital suffering from fatigue.
Mr Odinga went to the hospital Monday evening after presiding over a function and later feeling "some general exhaustion".
"I would like to inform you and the nation that the Prime Minister is unwell but he is in a fit and stable condition," said a statement from Mr Odinga's office.
He is been treated for fatigue and is expected to remain in hospital for a few days.
"After tests, doctors started treating him for fatigue. The doctors have further recommended complete bed rest for a few days and they will confine him in hospital for that period.
"During that period, the hospital will restrict access to him to ensure he gets the rest that he needs," said the statement.
His office, through spokesman Dennis Onyango, said the PM's doctors had reported that he was in a good enough "condition to come to office and work as usual if he feels".
"But they are not allowing that. They strongly recommend that he takes the rest."
His office said it will update Kenyans on Mr Odinga's condition in due course.
Mr Odinga had officiated at a function at the Nairobi Dam last evening, where he launched a project to reclaim the dam.
The US-based Global Peace Festival Foundation will remove water hyacinth that chokes the dam and turn it into organic fertiliser. The same organisation has been involved with efforts to clean the Nairobi River.
The PM is known to keep a hectic schedule and attends up to three functions a day.
On Monday, he attended a joint Parliamentary Group meeting of PNU and ODM at the Kenyatta International Conference Centre, Nairobi to lay strategy on ensuring the proposed constitution is passed at the referendum and in the evening he was chief guest at the Nairobi Dam event.
Mr Odinga has, in recent weeks, been actively campaigning in favour of a new constitution that will be subjected to a referendum on August 4. He spent two days in western Kenya last week wooing locals to vote for the document.
In April 2008, Mr Odinga underwent a laser eye surgery in Germany to correct an eye defect.