The deadly torrential rains had inundated vast tracts of rainforest nearby, leaving residents of the Darul Mukhlisin mosque and Islamic boarding school to search elsewhere for places of worship that had been less damaged.

"We have no idea where all this wood came from," said Angga, 37, from the nearby village of Tanjung Karang.

Before the disaster, the mosque bustled with worshippers -- locals and students alike -- attending daily and Friday prayers.

"Now it's impossible to use. The mosque used to stand near a river," said Angga. "But the river is gone - it's turned into dead land."

Village residents told AFP the structure likely absorbed much of the impact of trees and logs carried by the torrents, preventing even greater destruction downstream.

When AFP visited the site, the mosque was still encircled by a massive heap of timber -- a mix of uprooted trees and felled logs, likely from nearby forests.

By Friday, the death toll from one of northern Sumatra's worst recent disasters - including in Aceh, where a tsunami wreaked havoc in 2004 - had reached 995 people, with 226 still missing and almost 890,000 displaced, according to the National Disaster Mitigation Agency.

- Uncontrolled logging -

Authorities have blamed the scale of devastation partly on uncontrolled logging.

Environmentalists say widespread forest loss has worsened floods and landslides, stripping the land of tree cover that normally stabilises soil and absorbs rainfall.

Indonesia consistently ranks among the countries with the highest annual deforestation rates.

President Prabowo Subianto, visiting Aceh Tamiang district on Friday, assured victims the government was working to restore normalcy.

"We know conditions are difficult, but we will overcome them together," he said, urging residents to "stay alert and be careful."

"I apologise for any shortcomings (but) we are working hard," he said.

Addressing environmental concerns, Prabowo called for better forest protection.

"Trees must not be cut down indiscriminately," he said.

"I ask local governments to stay vigilant, to monitor and safeguard our nature as best as possible."

But frustrations were growing, with flood victims complaining about the pace of relief efforts.

Costs to rebuild after the disaster could run up to 51.82 trillion rupiah ($3.1 billion) and the Indonesian government has so far shrugged off suggestions that it call for international assistance.

Back in nearby Babo Village, Khairi Ramadhan, 37, said he planned to seek out another mosque for prayers.

"I'll find one that wasn't hit by the flood," he said. "Maybe some have already been cleaned. I don't want to dwell on sorrow anymore."