JAKARTA, Oct. 3 (Xinhua) -- The death toll from the devastating 7.5-magnitude earthquake followed by the tsunami has further jumped to 1,407, the disaster mitigation agency said on Wednesday.

More than 2,500 people were severely injured and are facing a shortage of necessary supplies after one of Indonesia's deadliest natural disasters struck the Sulawesi Island on September 28.

Authorities set a tentative deadline of Friday to find anyone still trapped under rubble, after which chances of finding survivors will dwindle to almost zero.

More than 25 countries have offered assistance after Indonesian President Joko Widodo appealed for international help.

Little of that, however, has reached the disaster zone, and increasingly desperate residents grabbed food and fuel from damaged stores and begged for help.

"There are still large areas of what might be the worst-affected areas that haven't been properly reached," the UN's humanitarian office said, and almost 200,000 people need urgent help.

The World Health Organization has estimated that across Donggala, some 310,000 people have been affected by the disaster.