The death toll from cyclone-induced floods and landslides in Indonesia passed 600 on Monday as rescuers battled to clear roads and improved weather conditions revealed the scale of a disaster that has killed nearly 800 people in Southeast Asia.

Indonesia, Malaysia, and Thailand have suffered devastation after a rare tropical storm formed in the Malacca Strait unleashed torrential rains and wind gusts for a week that hampered efforts to reach people stranded by mudslides and high floodwaters.

At least 176 have been killed in Thailand and three in Malaysia, while the death toll climbed to 604 in Indonesia on Monday with 464 missing, according to official figures.

Under sunshine and clear blue skies in the town of Palembayan in Indonesia's West Sumatra, hundreds of people were clearing mud, trees and wreckage from roads as some residents tried to salvage valuable items like documents and motorcycles from their damaged homes.

Men in camouflage outfits sifted through piles of mangled poles, concrete and sheet metal roofing as pickup trucks packed with people drove around looking for missing family members and handing out water to people, some trudging through knee-deep mud.

'Resilience and solidarity'

The government's recovery efforts include restoring roads, bridges and telecommunications services. More than 28,000 homes have been damaged in Indonesia and 1.5 million people affected, according to the disaster agency.

Indonesian President Prabowo Subianto visited the three affected provinces on Monday and praised residents for their spirit in the face of what he called a catastrophe.

"There are roads that are still cut off, but we're doing everything we can to overcome difficulties," he said in North Sumatra.

"We face this disaster with resilience and solidarity. Our nation is strong right now, able to overcome this."

The devastation in the three countries follows months of adverse and deadly weather in Southeast Asia, including typhoons that have lashed the Philippines and Vietnam and caused frequent and prolonged flooding elsewhere.

Scientists have warned that extreme weather events will become more frequent as a result of global warming.

In Indonesia's Palembayan, row after row of houses had collapsed, with crushed vehicles dotted along mud-laden streets and piles of motorcycles tangled up in heaps after being carried away by landslides and fast-flowing floodwaters.

Rescue teams were seen carrying away a body across a swathe of rural land now covered in debris, uprooted trees and household furniture.

"These used to be the houses of my parents, my brother, also my rice milling place, now all were gone," said Muhammad Rais, who lives in Palembayan and lost two family members. "We have nothing left."

Restoration underway in Thailand

In neighbouring Malaysia, 11,600 people were still in evacuation centres, according to the country's disaster agency, which said it was still on alert for a second and third wave of flooding.

The death toll rose slightly to 176 in Thailand on Monday from flooding in eight southern provinces that affected about 3 million people and led to a major mobilisation of its military to evacuate critical patients from hospitals and reach people marooned for days by floodwaters.

In the hardest-hit province of Songkhla, where 138 people were killed, the government said 85% of water services had been restored and would be fully operational by Wednesday.

Much of Thailand's recovery effort is focused on the worst-affected city Hat Yai, a southern trading hub which on November 21 received 335mm (13 inches) of rain, its highest single-day tally in 300 years, followed by days of unrelenting downpours.

Prime Minister Anutin Charnvirakul has set a timeline of seven days for residents to return to their homes.

The flood crisis has dented Anutin's popularity after only a few months in office as he prepares to call an election at the end of January, with criticism mounting over the government's slow response to the disaster.

Anutin on Monday said he was not concerned about loss of support. "I am only thinking about how to help the people," he told reporters.