83-year-old Kanja passed away this morning at PCEA Tumutumu Mission Hospital in Nyeri county where he succumbed of asthma and diabetes related complications.
His second born son Kanja Waruru told reporters at his Kirichu home in Nyeri Central sub county that his father died at 5am.
The former information minister who was also served as an assistant minister during the Moi regime retired active politics in 1997.
Family members began converging at the home for burial preparations.
President Uhuru Kenyatta has mourned the veteran politician, describing Kanja as a true son of Kenya and a patriot who contributed immensely to the struggle for the country's independence.
"Indeed, Kanja's name will be remembered alongside other icons of Kenya's freedom struggle who were ready to lay down their lives for the sake of our country's independence," President Kenyatta said.