Locals in Omuokiri village lynched the four after they allegedly stole a laptop and a smart phone. A video of the killings was posted on the internet on Saturday.
The video shows four naked and bloodied men, seemingly half unconscious, with tyres around their necks.
The University of Port Harcourt, in the state's capital, on Monday confirmed that three of the four were its students.
An investigation has been launched into the "reprehensible, barbaric act", Port Harcourt police spokesperson Ben Ugwuegbulam told NAN.