"The number of dead is now 905. There was a significant rise in bodies found in Gunungsitoli and Nias Selatan (South Nias) in the last few days," Wisnu Widjaya, a senior official at the national disaster agency, told Reuters.

"I think there will still be an increase in the number, but it will not be so much. Now that we have the heavy tools working in those areas, I reckon the total number will be over 1,000 but not exceeding 2,000," he said.

"The most casualties are in Gunungsitoli, and we have been working with heavy tools in that area for days now. I don't think there will be a dramatic increase."

The previous toll had been around 715 dead. Immediately after the earthquake, officials said they feared up to 2,000 may have been killed.

The United Nations, along with other relief organisations and military personnel from countries including Australia and the United States, are involved in aid operations in the area.

Relief workers on Nias say damage to roads and other infrastructure has made reaching isolated communities difficult. Many people are still sleeping in tents because of regular aftershocks.