Police officers reportedly fired tear gas at the protesters and physically assaulted them.
The protest, tagged "Occupy Owerri", was organised as a peaceful rally against "bad governance" and was scheduled to run from Monday till Sunday, December 24 as an expression of discontent with Governor Okorocha's policies.
While the Department of State Services (DSS) approved the rally on request by the group, the police had asked for it to be postponed till after the festive period.
According to a report by Premium Times, IPAD coordinator, Aku Obidinma, alleged that police officers fired tear gas at the protesters and physically assaulted them to end the protest on Monday.
He said, "We peacefully commenced our protest this morning from Wethral Road Roundabout in Owerri, Imo State, and were accosted by heavily armed policemen who demanded we stop because the commissioner of police did not approve the rally.
"We insisted that we must continue since the law did not say we needed his permission before we could embark on a peaceful protest.
"As we continued our match, the police descended on us and started beating up the protesters, firing tear gas, confiscated our placards and manhandled even the minors amongst us.
"Today is really a sad day for our democracy. Imo State has been turned into a terror zone. Governor Rochas Okorocha is now a full-blown dictator and he has as his accomplice the Imo State Police Commissioner, Mr. Chris Ezike, who is always ready to do his dirty jobs."
Despite the incident Obidinma remained defiant, insisting that the incident will not lead to the termination of the protest.
"We will in no distant time mobilise Imolites for a massive protest that will bring the government to its knees. We use this medium to call on the police authorities and the Presidency to quickly redeploy the Imo State Police Commissioner out of Imo State as he has lost the confidence of the people of the state."
In response to the incident, the state's police spokesperson, Andrew Enwerem, said the protesters were dispersed with tear gas because they didn't have the proper permit to stage the protest.
He said, "The duty of Police is to ensure security of lives and property, if they found themselves in friction with Police that is not out of place.
"Teargas is meant for human beings and not meant for animals. Before you protest you must get permission to March otherwise that will amount to unlawful assembly."
Governor Okorocha has been in the centre of public storms in recent months for a host of unpopular decisions that have earned him scorn.
In October, he unveiled a bronze-cast statue of South African president, Jacob Zuma, before unveiling another one for Liberian president, Ellen Johnson-Sirleaf.
Many Nigerians condemned the erection of the statues especially as there are several workers in the state who are still owed salaries and other entitlement.
Another reason why the protesters marched against the governor on Monday is his recent decision to appoint his sister, Ogechi Ololo, as the state's first Commissioner of Happiness and Purpose Fulfilment.