Screengrab from the video posted on YouTube.

Four students from the University of Port Harcourt, in southern Nigeria, were burned alive Friday by locals who accused them of being thieves. A horrific video of the scene has since surfaced online, angering their classmates, some of whom reportedly decided to get revenge by setting fire to the part of town where the young men were killed.

According to the Nigerian press, the four killed students were second-year undergraduates whom local residents in the Aluu neighbourhood of Port Harcourt accused of stealing a laptop computer and a Blackberry phone. A friend of the victims, meanwhile, told the BBC that they had gone to Aluu to try to collect money they were owed, and were mistaken for thieves.

The three-and-a-half minute video, which the police are using as part of their investigation, shows four young men lying on the ground, completely naked, with tyres around their necks. An angry mob beats them with sticks before setting them on fire. FRANCE 24 decided not to post the video here due to the highly disturbing nature of the images.

On Sunday, police arrested 13 people in connection with the case. However, this was not enough to calm Port Harcourt university students, who held a protest on Tuesday, blocking major roads on the edges of the university. Some reportedly turned to violence and set shops, houses and cars on fire in Aluu, which is adjacent to the campus, prompting many residents to flee. On Tuesday, the university closed its doors indefinitely . According to several of our sources, who preferred to stay anonymous out of fear for their safety, there have long been class tensions between the residents of Aluu and the university's students, who come from around the country and are generally wealthier.

This violence follows the killing of at least two dozen students at another Nigerian university , this time in the north of the country, earlier this month.