Police accused Moses Muigai Ngugi, who was arrested on Wednesday, of pretending to work for the National Intelligence Service, Kenya Bureau of Standards, Ethics and Anti-Corruption Commission, the office of the Director of Public Prosecutions and immigration department.
Police said they found cards showing he worked for the said agencies, two guns and 700 bullets his house in Syokimau, Machakos County.
He was arrested in Lavington area where police say he was meeting businessman Francis Mburu over the Ruaraka land saga.
Authorities claim he had told Mr Mburu he worked for NIS, which prompted the businessman to alert police.
After his arrest, he led police to his house, where the weapons, IDs and bullets were found, according to authorities.
Police have asked anyone with information that can help in their investigation of the suspect to report to Nairobi Area Flying Squad.
Nairobi Head of Directorate of Criminal Investigations Nicholas Kamwende said they would establish if Muigai was involved in any criminal activities.
He said detectives also wanted to establish how the suspect got his licence to own guns.