Controversial blogger Robert Alai is being held at Kamukunji Police Station in Nairobi.
He told the Nation that he was arrested Friday on Mombasa Road.
According to him, police cars fitted with ordinary number plates blocked his vehicle, before the officers jumped out with guns.
“They have not told me why I am under arrest. I do not know why I am here. They roughed me up. My shirt is torn,” said Mr Alai.
He added that the police had four cars when they arrested him.
Alai is active on social media, where he posts information on politics and social issues.
Recently, he posted photographs of the first family that were supposedly taken in a city hospital.
The caption suggested that a member of the first family had passed on.