Pandemonium broke out on Saturday, at the Ake Palace ground, venue of the State Congress of the All Progressives Congress (APC), organised by loyalists of former governor Ibikunle Amosun.
One person was feared killed while three others were injured.
The hoodlums, numbering over 20 stormed the venue of the congress in unmarked vehicles shooting sporadically at members of the party.
The hoodlums, who were also armed with cutlasses and other dangerous weapons, unleashed mayhem on party members who scampered for safety.
It was gathered that the thugs were allegedly led by a leader of a popular transport union.
The hoodlums attacked some of the party members and smashed the wind shield of several vehicles parked in front of the palace.
They carried out their actions in the full glare of police and other security agents.
Loyalists of the Amosun faction had gathered at the venue as early as 7.30a.m. for the inauguration of local government Exco members and also for the State Congress.