Mobile phone networks were jammed for at least an hour on Tuesday as millions of calls were made by people warning friends and relatives that the No?8 signal would be raised in the afternoon.
Calls from land lines to mobile phones and between different mobile networks were met with busy signals between 12.30pm and 1.30pm, the South China Morning Post found.
Messages sent via mobile phones were also delayed for more than two hours.
A message sent at 1.45pm to a mobile phone belonging to the same network did not reach the receiver until 4pm.
But telephone operators and the Office of the Telecommunications Authority (Ofta) denied that lines were jammed.
'Network traffic for some mobile operators was quite heavy around 1pm but none of the networks were jammed. People who couldn't get through at first just had to wait for a few minutes and call again,' an Ofta spokeswoman said.