At least 12 people have died and more than 600,000 households have been affected by the worst flooding in southern Thailand in decades, according to a government agency.

The death toll from the worst floods in decades in southern Thailand and northern Malaysia climbed to at least 12 on Saturday, authorities said, as tens of thousands of people were evacuated due to rising water levels in the past three days.

Thailand’s Meteorological Department has warned of heavy rain, flash floods, and waves up to 9.8 feet (3 meters) high across nine southern provinces due to strong monsoons.