Hundreds packed Nairobi's Anglican cathedral where Archbishop Eliud Wabukala said Easter services were overshadowed by "great and terrible evil" as police patrolled outside.

"These terrorists want to cause divisions in our society, but we shall tell them, 'You will never prevail,'" the archbishop said.

Flags were at half mast and although President Uhuru Kenyatta has vowed to retaliate "in the severest way possible", there have also been calls for national unity.     

Kenyatta said people's "justified anger" should not lead to "the victimisation of anyone" -- a clear reference to Kenya's large Muslim and Somali minorities.

Authorities meanwhile announced that they had identified one of the four dead Shebab gunmen as an ethnic Somali Kenyan national who was a A-grade pupil and law graduate – highlighting Al-Qaeda-linked Shebab's ability to recruit within Kenya.

Interior ministry spokesman Mwenda Njoka said it was "critical that parents whose children go missing or show tendencies of having been exposed to violent extremism report to authorities".

The militants attacked the university in the northeastern town of Garissa at dawn, lining up non-Muslim students for execution in what Kenyatta described as a "barbaric medieval slaughter".

The massacre, Kenya's deadliest attack since the 1998 bombing of the US embassy in Nairobi, claimed the lives of 142 students, three police officers and three soldiers.

Top Muslim leader Hassan Ole Naado also offered his condolences.

"Kenya is at war, and we must all stand together," said Naado, the deputy head of the Supreme Council of Kenya Muslims, saying the organisation was helping to raise money for the funerals of those killed and the medical costs of the scores of wounded.

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