A policewoman told Reuters the gunmen were likely to have taken hostages because many students remain trapped inside the campus. “Two guards who were manning the gate at the university have been killed,” she said. “We can hear gunshots from inside the compound but at this point we can’t tell who is shooting at who or what.”

Witnesses described a scene of carnage with a huge crater left behind following the blast at the gate.

Kenya's National Police Service said armed militants shot at campus guards to gain entry, triggering a "fierce shootout". The attackers still managed to get inside one of the student dormitories and some remain trapped inside. A spokesman for al-Shabaab said the group is inside the campus and has released Muslim students.

"We've killed many people; Kenyans will be shocked when the go inside," he was quoted by the BBC as saying.

One student said he could hear militants opening doors and asking those hiding inside if they were Muslim or Christian. "If you were a Christian you were shot on the spot," he said. "With each blast of the gun I thought I was going to die.

One student said he could hear militants opening doors and asking those hiding inside if they were Muslim or Christian. "If you were a Christian you were shot on the spot," he said. "With each blast of the gun I thought I was going to die.