The All Progressives Congress (APC) primary election is scheduled to commence by 12 noon and accreditation of voters is currently ongoing.
The security presence may not be unconnected to the clashes that have been recorded before the election day, in some parts of the state over a leadership crisis.
There are currently two factions of the APC in Osun. One faction is loyal to Gboyega Oyetola, the governor, who is seeking re-election.
The other faction is the backing of the minister of interior and former governor of the state, Rauf Aregbesola.
The contestants have been in a war of words before now.
One of the contestants, Moshood Adeoti, a former state chairman of the party, is the anointed candidate of the Minister of Interior, Ogbeni Rauf Aregbesola.
Also in the race is a former Deputy Speaker of the House of Representatives, Lasun Yusuf.