At least 38 university students were injured Friday near Nairobi after they mistook screams from a fellow student for signs of an extremist attack, a police official said Friday.

This is the fourth incident in which university students have been injured in a panic following the April 2 extremist attack on Garissa University in which 148 people died, most of them students. It was the second incident this week ahead of next week's first anniversary of the Garissa attack.

The stampede occurred following screaming in the library where a student stabbed another Kiambu County Commander James Mugera said. Mugera says students jumped out windows from high floors at Kenyatta University. The stabbed student was not seriously hurt and the assailant has been arrested, Mugera said.

One person died in December in Strathmore University after panic caused by a drill to test terrorism responsiveness. A University of Nairobi student was killed and 141 others injured during a stampede on April 12 when students mistook explosions from an electrical transformer that had short-circuited.  At least 20 students of Moi University in the western town of Eldoret were injured on Wednesday when a transformer blew up, according to local media reports.

Patrick Gathara, a political and security commentator said the incidents illustrate that people have little faith in government combating the threat of extremism.

"There is nothing that tells us the government has learnt from previous attacks; no reports and no inquiries on what went wrong," Gathara said.

Kenya has experienced attacks from the al-Qaida-linked Somali extremist group al-Shabab who have vowed retribution on Kenya for sending troops to Somalia to fight the militants.