The Kenyan Cabinet Secretary Joseph Ole Lenku has told a press conference that the government is determined to find the perpetrators of yesterday's attacks. The Somali terrorist group Al-Shabaab has claimed responsibility, according to a pro-Shabaab website.
Mr Lenku said an investigation had begun, and added:
"There is a line beyond which nobody should cross. The red line has since been crossed. Those engaging in incitement of the public will be firmly dealt with in accordance with the law."
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The man, who was in his 30s, has not been identified, while several other people are believed to have suffered serious injuries.
The Olympian was one of several sports stars who opened up to the prince during an event for his mental health charity Heads Together.
There will be sunny spells, with temperatures peaking at 23 Celsius (73F). However, Northern Ireland will experience frequent showers.