Somalia's Al-Qaeda-linked Shebab Islamists threatened Kenyan citizens with "another bloodbath" on Saturday, two days after their gunmen slaughtered 148 people at a university.
"We will, by the permission of Allah, stop at nothing to avenge the deaths of our Muslim brothers until your government ceases its oppression and until all Muslim lands are liberated from Kenyan occupation," the Shebab said in a statement.
"And until then, Kenyan cities will run red with blood... this will be a long, gruesome war of which you, the Kenyan public, are its first casualties."
The day-long siege on Thursday of the university in the northeastern town of Garissa was Kenya's deadliest attack since the 1998 bombing of the US embassy in Nairobi, and the bloodiest ever by the Shebab militants.
The Shebab, in an emailed statement written in good English, and which was confirmed genuine by a spokesman via telephone, described how they had specifically singled out non-Muslims to kill, gathering them together before executing them.
Survivors who hid from the attack have recounted how the gunmen called on people to come out of their dormitory bedrooms and lie on the ground face down, but then killed them.
A photograph seen by AFP from inside the building showed over 50 students killed lying down on the ground.
"The mujahedeen stormed the university compound and swiftly proceeded to the halls of residence where they had gathered all the occupants," the statement added.
"And since the attack targeted only non-Muslims, all Muslims were allowed to safely evacuate the premises before executing the disbelievers."
The statement also described what it called "unspeakable atrocities against the Muslims of East Africa" by Kenyan security forces, both in Kenya's northeastern ethnic Somali region and in southern Somalia, when Nairobi sent troops in 2011 to battle the Islamists.
The gunmen in Garissa wanted to "avenge the deaths of thousands of Muslims killed at the hands of the Kenyan security forces," the statement added.
The Kenyan government has vowed that it would not be "intimidated".
But the Shebab also warned the public they would be targeted in "schools, universities, workplaces and even in your homes" as they had elected the government.
"Choices have consequences; you chose your government out of your own volition so endure the consequences of your actions, for you will bear the full brunt of its follies," the statement read.
"Not only are you condoning your government's oppressive policies by failing to speak out against them, but are reinforcing their policies by electing them. You will, therefore, pay the price with your blood."