The United Nations' humanitarian chief said Thursday the powerful earthquakes that struck Indonesia have killed at least 1,100 people, while a government official said at least 777 people have been found dead.

During a press conference on natural disasters in the Asia-Pacific region, John Holmes said the latest figures received "suggest the death toll has risen already to 1,100" in the aftermath of Wednesday's 7.6-magnitude earthquake, which was followed by another earthquake Thursday morning.

The U.N. emergency relief coordinator and under-secretary-general for Humanitarian Affairs said he feared thousands more were trapped in the rubble of homes, hotels, hospitals and schools destroyed or badly damaged.

"There is a lot of emergency relief needed in all these cases," he said, describing a series of tsunami, earthquake and severe weather events that jolted the Region in the past week.