Anti-corruption activist Boniface Mwangi has been released after being briefly held by police in the capital, Nairobi.
Mr Mwangi said police officers had questioned him about a plot to lead what they said was a "revolution".
He told reporters he had no knowledge of any plan to organise a mass revolt.
Mr Mwangi has led several campaigns against state corruption, which have seen him arrested several times.
Mwangi said in a Facebook post after his release that Kenyans are angry, hungry and broke. "They feel like revolting against bad governance and corruption, and the government is afraid it's going to happen. Revolution is not treason."