Hong Kong - Australian visitors were warned Wednesday about Hong Kong's poor air quality in a travel alert issued by the Canberra government.

The alert warned that levels of air pollution "may aggravate bronchial, sinus or asthma conditions" and says people with heart or respiratory illnesses should take precautions.

It urges visitors with pre-existing conditions to reduce physical activity and outdoor activity on days when air pollution readings are high in the densely populated high-rise city of 7 million.

Around 80,000 people from Australia, New Zealand and the South Pacific islands visit Hong Kong every month, according to statistics from the tourism board.

The city is regularly shrouded in dense smog caused mostly by fumes from factories across the border in heavily industrialised southern China.

Critics say the Beijing-appointed government has been reluctant to tackle the issue and demand reduced cross-border factory emissions because of political sensitivities. (dpa)