Nairobi - Former Kenyan president Mwai Kibaki was flown to South Africa on Sunday evening for treatment.
The retired president, 85, was initially admitted to the Karen Hospital in Nairobi after falling ill at his home in Muthaiga.
He spent the whole day at the hospital before being flown outside the country for specialised treatment.
Kibaki's family confirmed his hospitalisation and asked Kenyans to pray for him.
"We expect him to return soon, and Kenyans will be informed of his progress as appropriate," the family said in a statement.
President Uhuru Kenyatta visited the former leader at Karen Hospital on Sunday, even as Kenyans took to social media to share messages of goodwill.
Former prime minister Raila Odinga, who ruled with Kibaki during his second and last term in office in the grand coalition government, said: "Ida Odinga (his wife) and I send good wishes to the former President HE Mwai Kibaki & his family following his hospitalisation."
Nairobi Senator Mike Sonko posted a prayer for the quick recovery of the retired President on his Facebook timeline.