Two elephants drowned during flash flooding in popular Thai tourist hotspot Chiang Mai, their sanctuary said Sunday, as local authorities evacuated visitors from their hotels and shops closed in the city centre.

Flash floods swept through a popular elephant sanctuary in northern Thailand on Thursday, forcing the evacuation of about 100 elephants and trapping dozens of tourists, amid urgent pleas for help.

Authorities and conservationists are rushing to rescue elephants, pigs and buffaloes from flash flooding in Thailand's northern Chiang Mai province, a senior official said on Friday.

Flooding in northern Thailand has forced many residents of the city of Chiang Mai and its outskirts to seek safety on higher ground, with members of the animal world under similar threat.

Several provinces in central Thailand braced for floods on Sunday after the Irrigation Department announced it was releasing water from a major dam after weeks of frequent heavy rain.

Chiang Mai, Thailand's northern city popular with tourists, was inundated by widespread flooding Saturday as its main river overflowed its banks following heavy seasonal rainfall. Authorities ordered some evacuations and said they were working to pump water out of residential areas and clear obstructions from waterways and drains to help water recede faster.