According to BBC, The storming of Garissa University College by militants is the worst attack on Kenyan soil since the 1998 US embassy bombing by al-Qaeda - 147 people have died and 79 have been wounded, some critically.
It follows repeated attacks inside Kenya by al-Shabab, which is affiliated to al-Qaeda.
The most audacious al-Shabab raid was on Westgate shopping centre in Nairobi in September 2013, when 62 civilians from 13 countries were among the 67 who died in a four-day siege.
BBC Somalia specialist Mary Harper looks at the tactics of the Islamist group, which controls rural areas of southern Somalia.
Why was Kenya attacked?
Al-Shabab says it has been at war with Kenya ever since Kenyan forces entered Somalia in October 2011 in an effort to crush the militants.