The Observatory said on Wednesday morning that it will issue the standby signal number one in the evening, as Super Typhoon Doksuri moved within 800 kilometres of the territory at lunchtime.

Local winds are expected to strengthen as Doksuri gradually moves towards coastal areas of eastern Guangdong and southern Fujian on Thursday and Friday.

The powerful storm had already reached the northern Philippines, toppling trees, knocking out power and dumping heavy rain as thousands sheltered with neighbours or in emergency evacuation centres.

Typhoon Doksuri was packing maximum sustained wind speeds of 175 kilometres an hour as it hovered over waters around Fuga Island, off the northern tip of the main island of Luzon, the state weather agency said in its latest update at 8am Hong Kong time.

The agency warned of "violent, life-threatening conditions" as severe winds and heavy rain pounded the lightly populated region. Doksuri had been a super typhoon as it swept across the Pacific Ocean on Tuesday, but weakened as it neared the Philippines.

Around 12,000 people were evacuated from their homes in Cagayan province, including 431 in the Babuyan islands, following warnings of three-metre high storm surges, provincial disaster official Ruelie Rapsing told the AFP news agency.

Doksuri is expected to weaken further as it moves across the South China Sea towards southeastern China. (additional reporting by AFP)