Watch: Satellite images reveal Indonesia's Sulawesi Island after earthquake, tsunami

Indonesian authorities on Tuesday raised the death toll to 1,234 for the 7.5-magnitude earthquake and subsequent tsunami that hit Sulawesi island on September 28. Sutopo Purwo Nugroho, spokesperson for the National Agency for Disaster Management, said at a press conference in Jakarta that 799 people with serious injuries have been admitted to different hospitals.

He added that 26 countries and two international organizations have offered assistance, but did not provide details on the NGOs that are working in the rescue operations and medical services on the ground.

Authorities raised the death toll on Tuesday after rescue teams were able to enter the areas that had been inaccessible since a 6.1-magnitude tremor struck the region on Sep 28, killing one person and wounding 20, followed by a 7.5-magnitude earthquake and the tsunami.

Sutopo said that there are still areas in the central region of Sulawesi that are difficult to access. Colonel Muhammad Thohir of the Indonesian Army said there are some areas that rescuers still cannot reach such as some districts in Donggala where authorities need to send aid via helicopter.

Palu is the capital of the province of Central Sulawesi with a population of about 350,000. It is located near Donggala district, which has a population of about 277,000. These areas are most affected by the disaster.

Col Thohir said gasoline and water supplies are being transported to the island, but they are still insufficient for the tens of thousands of affected people. Authorities are also working to restore electricity and telecommunications services as well as to reopen affected roads on the island.

According to the Indonesian authorities, priorities include sending food to those in need, conducting mass burials of victims and guaranteeing the security of the airport, which is expected to start receiving commercial flights on Wednesday.

On Lombok, at least 557 people died and over 400,000 were displaced by earthquakes between magnitude-6.3 and 6.9 that shook the island between July 29 and August 19. Indonesia sits on the so-called Ring of Fire of the Pacific, an area of great seismic and volcanic activity in which each year there are about 7,000 earthquakes, mostly moderate.