Hong Kong - Hong Kong is on standby to raise its alert level over swine flu to emergency as soon as necessary, the city's health secretary said Thursday.

York Chow said the city's alert level would be raised from "serious" to "emergency" as soon as the World Health Organisation put its own alert up from the current five to six, the highest level.

As a government committee met to draw up measures against the threat of a pandemic in the city of 7 million, Chow said: "We will raise our alert level to the highest level - emergency - as soon as it is required.

"Once the WHO announces the pandemic alert is raised to level six or there is a first confirmed case of swine flu in Hong Kong, we will definitely raise our alert level to emergency immediately."

Hundreds of thousands of US dollars are meanwhile being invested in a cleanliness campaign across Hong Kong to encourage people to observe good hygiene to help ward off the threat of a pandemic.

No cases of swine flu have so far been detected in Hong Kong which is at an increased risk from the pandemic because it is so densely populated, according to chief executive Donald Tsang.

Hong Kong has developed a sophisticated system of measures to combat disease after suffering human deaths from bird flu in 1997 and Severe Acute Respiratory Syndrome or SARS in 2003.