Reports said more than 30 students have fled to safety while others who escaped with injuries are receiving treatment for gunshot wounds. Kenya Red Cross and other humanitarian organizations are the at scene to help in the rescue services.

Ismail Abdikadir, an activist based in Garissa, said the gunmen went into the university posing as worshipers for morning prayers.

"There were many students who were for the morning prayers. There could be many casualties," Abdikadir said by telephone.

The attack started from the Mosque inside the university where the attackers shot at worshippers indiscriminately. Students who escaped the attack said there were at least five attackers. Many other students and teachers were still being held hostage by 8:30 am local time (0530 GMT).

Witnesses said ambulances were carrying casualties to Nairobi.

Local security officials said there had been threats on the institutions there from terror group.

"We had the threats earlier and had alerted the institutions here," said a security official who asked not to be named.