Citybus and New World First Bus say due to the Gale Signal No.8 being force, most of their buses will not be running.

"All overnight routes of Citybus and NWFB are suspended," it said in a statement issued at 5 am on Thursday. "Except for Citybus Route S1 and B3X providing limited levels of services from their first departures, all daytime routes will be suspended."

Severe Tropical Storm Ma-on is now heading away from Hong Kong towards the coast of western Guangdong, after having passed Hong Kong to the southwest.

The Observatory says the number 8 signal is expected to be in force until 9 am.