President Xi Jinping has extended condolences to his Philippine counterpart Rodrigo Duterte after a severe tropical storm ravaged the southern Philippines, Foreign Ministry spokeswoman Hua Chunying said on Tuesday.

"China is willing to provide all the assistance we can for the Philippines' disaster relief work, and we believe that people in the storm-hit areas can overcome difficulties and rebuild their hometown under the leadership of the Philippine government," Hua said in Beijing.

Tropical Storm Tembin started lashing parts of the island of Mindanao on Friday, triggering massive floods and mudslides in the region which left more than 160 people dead.

On Tuesday, the powerful storm was downgraded to a tropical depression and failed to make landfall in Vietnam.

Hundreds of thousands of people in Vietnam's Mekong Delta had been evacuated as the region braced for the arrival of Tembin.

Weather forecasters had expected the delta's southern tip to be in Tembin's path, and said heavy rain and strong winds starting on Monday night could cause serious damage in the vulnerable region, where facilities are not built to cope with such severe weather.

By Tuesday morning, the storm was downgraded and forecasters said it would not make landfall.

The storm was expected to dissipate over the Gulf of Thailand later.

Over the weekend, Tembin unleashed landslides and flash floods that killed at least 164 people and left 171 others missing in the Philippines, according to Romina Marasigan of the government's main disaster-response agency.

Initial reports from officials in different provinces placed the overall death toll at more than 230, but Marasigan warned of double counting amid the confusion in the storm's aftermath and said the numbers needed to be verified.

More than 97,000 people remained in 261 evacuation centers across the southern Philippines on Monday, while nearly 85,000 others were displaced and staying elsewhere, the National Disaster Risk Reduction and Management Council said.

The hardest-hit areas were Lanao del Norte and Lanao del Sur provinces and the Zamboanga Peninsula. Tembin hit the Philippines as a tropical storm but strengthened into a typhoon before blowing out of the country on Sunday into the South China Sea toward Vietnam.

Tembin was among a series of disasters to hit the predominantly Roman Catholic Philippines at the peak of Christmas preparations.

AP and Xinhua contributed to this story.