Taiwan warned Sunday that Typhoon Tembin was likely to return as people struggled to clear mud-filled homes after the storm pounded the south of the island with the heaviest rains in more than a century.

The storm appeared to be heading back towards Pingtung county where people were still reeling from the flooding sparked by Tembin when it swept across the southern tip of the island Friday.

Tembin weakened to a tropical storm after moving out to sea the same day but the Central Weather Bureau said it had intensified into a typhoon again Sunday.

"Tembin regained strength and became a typhoon again early this morning. It was moving east-southeasterly," the bureau said.

Although the typhoon was still hundreds of kilometres (miles) from the island, the bureau predicted downpours in the south and southeast and called on people there to take precautions.

On its current track, Tembin was forecast to make landfall again in Pingtung and move northward off the east coast.

The storm's unusual movement was largely affected by Typhoon Bolaven, which was gaining momentum and churning towards southern Japan and predicted to hit Okinawa. Bolaven was about 800 kilometres (500 miles) east of Taiwan.

Tembin, which forced more than 8,000 people to evacuate their homes islandwide, unleashed torrential rain in Pingtung county that was described as the worst in more than a century.

Weather bureau data indicated Pingtung as a whole received 724 millimetres (29 inches) of rain since Wednesday, while the township of Hengchun saw more than 600 millimetres of rainfall on Friday alone.

Television images Sunday showed soldiers helping people remove thick mud from their homes in the flooded area.

As of 0330 GMT, Typhoon Tembin was around 400 kilometres southwest of the main southern city of Kaohsiung. With a radius of 180 kilometres, the typhoon was packing gusts of up to 119 kilometres per hour and moving east-southeast at eight kph.