Ojerinde, who was the Principal Private Secretary to Edo State Governor Adams Oshiomhole and Deputy National Secretary of the Nigeria Labour Congress, was killed in his Benin residence by gunmen in May.
President Goodluck Jonathan ordered the IG to ensure that his killers were apprehended.
Abubakar announced the arrest of the suspects after addressing Police Zone 5 officers in Benin ahead of Saturday’s Edo State governorship election.
“I can confirm that the police have arrested four suspects in connection with the killing of Oyerinde and investigation is continuing.
However, he did not give further details of the breakthrough in the police investigations.
But he took exceptions to the ultimatum given the police by Governor Adams Oshiomhole of Edo State who gave the police 14 days to bring the killers of Ojerinde to book.
“You can’t just give the police 24 hours to do a miracle. We have to investigate and look at all the facts of the matter before we can come to a conclusion,” Abubakar said.
On Oshiomhole’s rejection of the police investigation report into the alleged attack on his convoy on Auchi-Warrake Road in April, the police chief said the force had the constitutional responsibility to conduct investigations.
He said, “We have come out with our report and we stand by the report of our investigation until otherwise proven.
“Investigations were conducted by the police. Investigations are made based on the preponderance of evidence. We were not there. But we have conducted our own investigation and facts available to us led to the conclusion we made.
“And based on their statements, the police came to the conclusion we arrived at.”
“Whether anybody dismisses it or not, that is not the issue.
“The facts available to us now inform us of what we have said, and if any body has anything contrary, he should be able to come forward to defend it.
“We cannot allow people to sit down and make statements they don’t have facts about.
“If you have evidence to say it was A, B, C or D, you must be ready to prove it.”
He warned said it was irresponsible for some highly placed Nigerians to public statements which they cannot back with facts.