If we believe the Kenyan security agencies:

Security agencies worry about new terrorist threats in Kenya

Kenyan and Western security services are racing against time to foil new planned terror attacks in Kenya barely three weeks after the Westgate attack.

Much of the investigations are now focused on the underground activities of a shadowy militant organisation called Al-Hijra, led by Sheikh Iman Ali, a Kenyan preacher now hosted by al-Shabaab in Somalia.
...
“We in the EU are aware of the threats posed by Al-Hijra and its affiliates. The new plots are grave and warrant a lot of attention, but we have no intention at this stage to elevate them into a full-blown travel alert. We are sensitive to Kenya and its economic needs and we are all working together to foil possible future attacks,” a senior European diplomat told the Sunday Nation.
...
“Westgate was a complex operation that was carried out with low-tech means and certainly much more difficult to detect or disrupt than the iconic suicide bomber. It is also much easier to replicate,” Matt Bryden, a regional analyst and director of Sahan Research, told the Sunday Nation
...
“There have been extensive arrests in Kenya, on the border with Somalia, and even as far as Uganda and Tanzania. I believe good progress is being made. But we must complement these measures by strengthening our capacity; improving our intelligence gathering and law enforcement systems and improving co-operation with the public.”
...
“Al-Hijra has been under surveillance for a number of years and the Kenyan state has accumulated enough intelligence on its ideological leaders to disrupt the movement. For some reasons, there is reluctance to provide classified intelligence to the law enforcement agencies for effective prosecutions. And this ought to change.”
http://www.hiiraan.com/news4/2013/Oc..._in_kenya.aspx