Singapore: The death toll from a fortnight of extreme weather in southern Asia has passed 1200 – a figure set to rise as rescuers sift through mud and debris for hundreds of people still missing.

Floods and mudslides from simultaneous tropical storms late last month have wiped out entire villages in Sri Lanka and across the Indonesian island of Sumatra.

In southern Thailand, the city of Hat Yai has also experienced what authorities there have described as a one-in-300-year rain event.

Faced with rising death tolls from the latest events, Indonesian President Prabowo Subianto has called for more action on climate change, while Sri Lankan President Anura Kumara Dissanayake says it is the first time such a disaster has struck the entire country.

The principal cause of the Indonesian devastation, Cyclone Senyar, formed in the middle of last week over the Malacca Straight – a rare meteorological event – and crashed into the Sumatran coast at Langsa, where a month’s rainfall (382 millimetres) fell in a 24-hour period from November 25.

More than 659 people have died in Aceh, North Sumatra and West Sumatra, while a further 500 may be missing under floodwaters and mud.

The rain was exacerbated by Senyar’s interplay with Typhoon Koto, another system that was over the Philippines, according to Indonesia’s Meteorology, Climatology, and Geophysics Agency.

Senyar veered back over the strait in a weaker form from November 27 towards Malaysia, where three people were killed and almost 12,000 were forced into evacuation centres.

In Sri Lanka, where some 30,000 Sri Lankans died in the 2004 Boxing Day tsunami, Dissanayake called the latest and still-unfolding catastrophe the “largest and most challenging natural disaster” in the country’s history.

Cyclone Ditwah spent more than two days tracking the entire east coast from late last week, killing at least 390 people and leaving hundreds more missing.

The United Nations estimates that about 1 million people spread over each of Sri Lanka’s 25 districts have been affected, while about 180,000 people have been forced to shelter in government safety centres.

“This is the first time the entire country has been struck by such a disaster,” Dissanayake said.

In Indonesia, almost 1.5 million people, more than 500,000 of them displaced, have been affected across 48 regencies in Sumatra, according to the National Disaster Management Agency.

“We need to confront climate change effectively,” Prabowo said during a visit to affected areas on Monday.

“Local governments must take a significant role in safeguarding the environment and preparing for the extreme weather conditions that will arise from future climate change.”

Water is receding in Thailand, where at least 181 people have died across nine southern provinces, mostly in Songkhla. Hat Yai, that province’s administrative centre, received more than 600 millimetres of rain over three days from November 19.

Residents there have criticised the new national administration of Anutin Charnvirakul for not providing what they felt were appropriate warnings about the severity of the weather system and impending floods.

Anutin, who has promised fresh elections for early next year, has apologised for the government’s performance but also remained defiant.

“There is no need to say they’re wrong because everyone has the right to speak,” he told local media. “But when it comes to our work in Hat Yai – helping people and implementing measures – the government is confident we are on the right track and doing everything that must be done.”

The devastation wrought by the weather in Indonesia, Sri Lanka, Thailand and Malaysia follows back-to-back cyclones in the Philippines early last month and flooding in Vietnam that, combined, left hundreds of people dead.

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