"No amount of precaution or safety measures will be able to guarantee your safety, thwart another attack or prevent another bloodbath from occurring in your cities," said Al Shabaab in a statement released on Saturday.
The statement comes a day after hundreds of Christian and Muslim residents from the Kenyan town of Garissa, 150 kilometers from the border with Somalia, held a march and a rally to protest against the Al Shabaab militant group after Thursday's attack.
The demonstration also sought to draw attention to a perceived lack of protection from Kenyan security services following similar terrorist attacks from Al Shabaab, notably the siege of a Nairobi shopping center in 2013 which left at least 67 dead and 175 wounded.
Hundreds of students fled the campus as the attack began, in which non-Muslim students were singled out as targets. The assault came to an end when Kenyan soldiers stormed the dormitory where the hostages were being held and opened fire on the terrorists, who detonated their suicide vests.