Banda Aceh (AFP) — Governments and aid groups in Indonesia and Sri Lanka worked Tuesday to rush aid to hundreds of thousands stranded by deadly flooding that has killed over 1,200 people in four countries.

Torrential monsoon season deluges paired with two separate tropical cyclones last week dumped heavy rain across Sri Lanka and parts of Indonesia’s Sumatra, southern Thailand and northern Malaysia.

Climate change is producing more intense rain events because a warmer atmosphere holds more moisture, and warmer oceans can turbocharge storms.

The floodwaters have now largely receded, but the devastation means millions of people are living in shelters and struggling to secure clean water and food.

In Indonesia’s Aceh, one of the worst-affected regions, residents told AFP that survivors who could afford to be stockpiling supplies.

“Road access is mostly cut off in flood-affected areas,” 29-year-old Erna Mardhiah said as she joined a long queue at a petrol station in Banda Aceh.

“People are worried about running out of fuel,” she added from the line she had been in for two hours.

The pressure has caused skyrocketing prices.

“Most things are already sky-high... chilies alone are up to 300,000 rupiah per kilo ($18), so that’s probably why people are panic-buying,” she said.

On Monday, Indonesia’s government said it was sending 34,000 tons of rice and 6.8 million liters of cooking oil to the three worst-affected provinces, Aceh, North Sumatra and West Sumatra.

“There can be no delays,” Agriculture Minister Andi Amran Sulaiman said.

But Alfian, a resident in Banda Aceh, told AFP the government had been “very slow, especially in ensuring basic necessities.”

Aid groups said they were working to ship supplies to affected areas, warning that local markets were running out of essential supplies and prices had tripled already.

“Communities across Aceh are at severe risk of food shortages and hunger if supply lines are not reestablished in the next seven days,” charity group Islamic Relief said.

A shipment of 12 tons of food from the group aboard an Indonesian navy vessel was due to arrive in Aceh on Tuesday.

At least 659 people were killed in the floods across Sumatra, and 475 are still listed as missing. A million people have evacuated from their homes, according to the disaster agency.

Survivors have described terrifying waves of water that arrived without warning.

In East Aceh, Zamzami said the floodwaters had been “unstoppable, like a tsunami wave.”