Students of the Garissa University College take shelter in a vehicle after fleeing from an attack by gunmen in Garissa, Kenya, April 2, 2015. [Photo/IC]

The organisation said it is leading a medical evacuation and working with the health ministry to deploy surgeons to the grounds. It said it is evacuating casualties to the Garissa Provincial General Hospital where it is organising a blood donation drive with the ministry.

The team is further organising for the severely injured to be airlifted to Nairobi and has set up a psychological support desk for victims and families.

Witnesses say the gunmen went into the university as students were going for morning prayers. Those calling from inside the university say there are many casualties.

The attack comes after three universities had issued security alerts barely a week before the latest attacks, informing students and staff of new security measures while cautioning people within their campuses to be extra vigilant.

Kenyatta University, the University of Nairobi, and the United States International University in the capital Nairobi had warned the students there was credible intelligence of possible terrorist attacks of a university or college in Kenya.

"Intelligence reports indicate that the Al-Shabaab terror group is planning retaliatory attacks on vital installations in Nairobi, including a major university," the University of Nairobi Chief Security Officer W.M. Wahome said in its memos to students dated on March 25.