KUALA LUMPUR - Tens of thousands of Indonesians are struggling to rebuild their lives a year after a powerful earthquake and tsunami caused widespread devastation, with many still homeless and schools unable to reopen, aid groups said on Saturday.

The city of Palu on the island of Sulawesi was devastated by a 7.5-magnitude earthquake and a tsunami it unleashed on Sept. 28 last year, killing more than 4,000 people.

Humanitarian aid poured in after the disaster but local charities said a year on, survivors were still living in makeshift shelter and children could not return to schools as they called for rebuilding efforts to be stepped up.

"Children long for a sense of normality," said Dino Satria from the charity Save the Children Indonesia, which estimated that two-thirds of about 1,300 local schools were still damaged.

"They continue to be traumatized by the disaster as they cannot go back to schools, cannot return to their normal routine as a way to help them overcome their trauma," the operation director told the Thomson Reuters Foundation by phone from Palu.

Satria urged authorities to speed up reconstruction efforts, but a local education official said the task was enormous without sufficient funding, although rebuilding schools was a top priority.

"Sadly, we are restricted by a lack of funds. I need an additional $11 million just to rebuild the schools in Palu City. The task at hand is immense," Ansyar Suitiadi, the head of education in Palu, said in a statement from Save the Children.

The Indonesian Red Cross estimates 57,000 people in Palu are homeless, and continue to live in camps and temporary shelters.

"We are hoping the government will redouble their efforts to identify settlement areas and help thousands of families," Jan Gelfand, Indonesia head of the International Federation of Red Cross and Red Crescent Societies said in a statement.

The Southeast Asian nation of 260 million, which sits on the seismically active Pacific Ring of Fire, often experiences deadly earthquakes and tsunamis.

The twin tragedies that hit Palu last year came one month after the Indonesian resort island of Lombok was rocked by quakes that flattened villages and killed more than 500 people.

Fifteen years ago, a quake off Sumatra island triggered a tsunami across the Indian Ocean that killed 226,000 in 14 countries, more than 120,000 of them in Indonesia.