HONG KONG, Sept. 23 (Xinhua) -- The Hong Kong Observatory issued No. 8 Northwest Gale or Storm Signal for super typhoon Ragasa on Tuesday afternoon.

No. 8 signal was the third-highest warning under Hong Kong's weather system, which has five rankings for typhoons.

The observatory said that Ragasa was centered about 380 km southeast of Hong Kong at 2 p.m. local time. According to the present forecast, it will maintain super typhoon intensity and be closest to the vicinity of the Pearl River Estuary on Wednesday morning, with local winds strengthening further.

Under the influence of storm surge, the water level is forecast to rise by around 2 meters over the coast of Hong Kong on Wednesday.

John Lee, chief executive of the Hong Kong Special Administrative Region (HKSAR), said that all emergency units of the government are on standby to ensure the safety of the public.

According to the Hospital Authority, three people have sought medical treatment at public hospitals as of 7:50 p.m. local time Tuesday.

The Home Affairs Department has so far opened 48 temporary shelters in various districts across the city, and 599 people have sought refuge at the shelters.

The MTR Corporation, Hong Kong's railway operator, has suspended part of its high-speed rail services due to the typhoon, while airline Cathay Pacific said it expects to cancel more than 500 flights from Tuesday to Thursday.

The Hong Kong Observatory said it will consider upgrading the No. 8 typhoon signal to No. 9 between 1 a.m. and 3 a.m. on Wednesday as Ragasa gets closer to the city.