The death toll mounted to over 600 from floods and landslides caused by torrential rains across three countries in Southeast Asia, Reuters reported Sunday, citing regional officials, as relief efforts for tens of thousands of displaced people continued over the weekend.

Indonesia, Malaysia and Thailand faced large-scale devastation after a rare tropical storm formed in the Malacca Strait, fueling heavy rains and wind gusts for a week. There were 435 deaths in Indonesia, 170 in Thailand, and three deaths reported in Malaysia.

Rescue and relief officials in the Southeast Asian countries were still trying to get access to many flood-hit areas on Sunday even as flood waters receded and tens of thousands of people were evacuated across the three countries. Over 4 million people have been affected - nearly 3 million in southern Thailand and 1.1 million in western Indonesia, according to official statistics.

The death toll surged in Indonesia to 435 on Sunday, up from 303 on Saturday, official data uploaded on a government website showed, as officials compiled reports of casualties and damage pouring in from the western island of Sumatra, where three provinces had been devastated by landslides and floods after the rains.

Many areas were cut off due to blocked roads, while damage to telecommunications infrastructure has hampered communication. Relief and rescue teams used helicopters to deliver aid to people in areas that could not be reached by road.

According to official figures, 406 people were still reported missing and 213,000 displaced.

Thailand's Ministry of Public Health reported the death toll from flooding in southern Thailand at 170, an increase of eight from Saturday, and 102 injuries. Songkhla Province had the highest number of fatalities at 131.

Hat Yai, the largest city in Songkhla, received 335 mm (13 inches) of rain last Friday, its highest single-day tally in 300 years, amid days of heavy downpours.

In neighboring Malaysia, there are still about 18,700 people in evacuation centers, according to the country's national disaster management agency.

Meteorological authorities lifted tropical storm and continuous rain warnings on Saturday, forecasting clear skies for most of the country.