A horrific video of the killings was posted on the YouTube video-sharing website.
One of those arrested was a traditional ruler in the Aluu community of Port Harcourt, police said, urging students from the University of Port Harcourt (Uniport) not to seek revenge.
The students had been accused of stealing laptops and mobile phones.
The video shows four men stripped naked, with tyres around their necks, being beaten by a mob with wooden sticks, before being set on fire.
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