Kenya's telecommunications regulator on Wednesday told mobile phone users to ignore swirling rumours that receiving calls from some numbers appearing in red can cause brain haemorrhage.
A text message sent around since late Tuesday and seen by AFP said 27 people had died after they picked calls from numbers listed in the SMS.
"Please inform all your friends and relatives soon, it's urgent," read the text.
But the Communications Commission of Kenya (CCK) said the message should be dismissed.
"Upon analysis of the messages, the commission has established the warnings are a hoax generated by unscrupulous people bent on causing fear and despondency among members of the public," a statement said.
"In addition, the alleged haemorrhage due to high frequency has no technical basis whatsoever."
The CEO of Kenya's largest mobile phone company Michael Joseph said the text message was "a popular urban myth that has been perpetuated, especially in some Asian markets."