The party says Elton Mangoma, who is in charge of power and gasoline supplies in the troubled economy, was released later Wednesday. He allegedly said at a political meeting in May: "Mugabe die. Mugabe go."
It is an offense under sweeping security laws to undermine the authority of the 88-year-old longtime ruler Mugabe.
Insult offenses, with a penalty of a fine or imprisonment, are common. A Zimbabwean salesman spent four months in jail earlier this year after being found with cartoons of a naked Mugabe on his mobile phone.
Mangoma was cleared last year on corruption charges he says were a political ploy.