Nigerian mobile phone users have been anxiously checking who is calling them before answering them in recent days.
Mobile phone use has taken off in Nigeria in recent years
A rumour has spread rapidly in the commercial capital, Lagos, that if one answers calls from certain "killer numbers" then one will die immediately.
A BBC reporter says experts and mobile phone operators have been reassuring the public via the media that death cannot result from receiving a call.
He says that in such a superstitious country unfounded rumours are common.
A list of alleged killer numbers has been circulated but no-one is reported to have died from answering the phone.
The BBC's reporter in Lagos, Sola Odunfa, says that the current scare story is reminiscent of a rumour that spread a few years ago that a handshake could cause sexual organs to disappear.
That rumour turned to tragedy as mobs rounded on people accused of making organs disappear.
Despite the massive public interest, no-one was found to have lost their organs.