- Both Taiwan and the Philippines are seeing large amounts of rain as Typhoon Gaemi moves through the area, causing widespread flooding.
- The typhoon was originally expected to hit further north, but the mountains of northern Taiwan steered it slightly south towards the city of Hualien.
The Philippines is in a race against time to contain an oil spill after a tanker carrying close to 1.5 million litres (400,000 gallons) of industrial fuel capsized and sank off the country's coast, officials say.
There are fears the "enormous" spill - which is already stretching out over several kilometres - could reach the shore of the capital, Manila, Coast Guard spokesman Rear Admiral Armando Balilo told reporters.
The ship was one of two which sank in the region on Thursday, with the second going down just off Taiwan's south-western coast.
Both Taiwan and the Philippines are seeing large amounts of rain as Typhoon Gaemi moves through the area, causing widespread flooding.
The typhoon made landfall in mainland China on Thursday evening local time, with authorities declaring the highest tier disaster warning.
It first struck Taiwan on Wednesday evening, killing three as it made its way across the island.
Four counties and cities in Taiwan saw more than a thousand millimetres of rainfall during a 14-hour period ending Thursday afternoon.
The Philippines avoided a direct hit by Gaemi, but the storm intensified seasonal monsoon rains, triggering widespread flooding across large swathes of Metro Manila and its suburbs.
Despite the heavy rains, the MT Terra Nova, which sails under the Philippines' flag, had not broken any regulations around travelling in heavy weather, according to Rear Admiral Balilo.
The tanker was heading for the central Philippine city of Iloilo when it sank, with 17 crew members on board.
One died, but 16 were successfully rescued, officials said. Authorities are investigating whether bad weather was a factor.
The Coast Guard is now "racing against time" to contain the spill, which could - if all of the oil leaks - become the biggest in the country's history.
0:50People swim, drive and wade through deep floodwaters in Manila
High winds and rough seas were hampering their attempts, however.
Even if they managed to avoid a catastrophe of that magnitude, Rear Admiral Balilo said it would "definitely affect the marine environment".
Pando Hicap, chairman of the local fishing group Pamalakaya, said the spill was "alarming" because fishermen's livelihoods were "dependent on the waters".
"They don't have any alternative," he told news agency AFP.
Meanwhile, to the north in Taiwan, all nine sailors were initially reported missing after their Tanzania-flagged cargo ship Fu Shun went down.
The Myanmar nationals were forced to abandon the sinking ship, Hsiao Huan-chang, head of the fire agency, told AFP.
"They fell into the sea and were floating there," he said.
The first attempts to reach the crew, who were wearing lifejackets, were hampered by the low visibility and high winds, but by the end of Thursday three had been reported rescued.
EPA-EFEA Philippine Coast Guard handout photo shows the coastguard searching for a capsized tanker
The typhoon was originally expected to hit further north, but the mountains of northern Taiwan steered it slightly south towards the city of Hualien.
The typhoon is expected to weaken as it tracks over the mountainous terrain of Taiwan before re-emerging in the Taiwan Strait towards China.
A second landfall is expected in the Fujian province in southeastern China later on Thursday. Several rail operators in China have also suspended operations.