"It's awful, I felt I couldn't breathe when I woke up this morning," said one saleswoman in her late 20s.

A recent survey found nearly 40 percent of children in the tiny territory suffered from a respiratory disease which experts have linked to deteriorating air quality.

Pollution levels were worst in the central business district, home to many local and international companies. The light brown haze blotted out the city's famous Victoria Habour and skycrapers loomed like ghosts in the tepid morning light.

The air pollution index hit 118 in the central business district just before midday, an official at the Environmental Protection Department said. It was almost as bad in the densely populated shopping belts of Mongkok and Causeway Bay.

Government officials said the pollution was from local factories, vehicles and China's fast-growing Pearl River Delta. Typhoon Sinlaku, which was churning closer to southern China, also affected local weather patterns.

"The air typically hangs still just before the arrival of typhoons, and this traps the air pollutants and they cannot disperse," the environment department official said.

Hong Kong's smog was unlikely to lift until the typhoon makes landfall in southern China on Sunday, he said.

Hong Kong's air pollution problem has grown steadily worse in recent years, caused in part by the territory's large fleets of diesel-powered vehicles and rapid economic growth in China's Guangdong province, just north of Hong Kong.

Business executives have stepped up pressure on Hong Kong's government to clean up the bad air, which they say is turning off potential investors and foreign talent who might otherwise want to relocate and work here.

Authorities in Hong Kong and southern China have repeatedly said they would tackle cross-border pollution but few concrete measures have emerged.