Children and teachers cleaned up debris swept into classrooms by last week's tsunami as schools reopened Monday in the resort town hardest hit by the killer waves.

Meanwhile, the official death toll from the disaster was revised downward to 600, with 70 missing, the National Disaster Management Coordinating Board said. The earlier toll was 668 dead and more than 280 missing.

"There was some double counting and incorrect data," agency official Maman Susanto said in explaining the new figures.

Attendance at school Monday was low. Thousands of children, parents and teachers are still grieving dead loved ones or have fled the town, either to temporary camps in the hills or to relatives' houses.

"I am still afraid," said Yusi Sundari, one of only three pupils who turned up at Elementary 5 school, just 300 yards from the beach. She joined teachers with mops and brushes clearing up sand and other debris washed into the building by the waves.

"My mother told me to be careful and if people warn of a tsunami I must run away," she said.

In the hills above the town, teachers and students were also cleaning a school used by hundreds of people as a temporary evacuation camp following the July 17 tsunami, triggered by a magnitude-7.7 quake off Java's southern coast.

The waves pummeled a nearly 200-mile stretch of coastline.

Indonesia's Sumatra island was home to more than half of the 216,000 people killed in the 2004 Asian tsunami, and questions have been raised as to why the government was not able to warn coastal communities before this month's tsunami.

The government started setting up an early warning system after the 2004 tsunami, but it is still in the initial stages and does not cover Java island, home to more than half of Indonesia's 220 million people.

Indonesia is on Pacific "Ring of Fire," an arc of volcanoes and fault lines encircling the Pacific Basin. The sprawling country of 18,000 islands is rocked by earthquakes on a near daily basis.

On Sunday, four earthquakes strong enough to be felt by people hit the country, according to the Meteorological and Geophysics Agency. The strongest — measuring 6.1 magnitude — struck off Sulawesi island, prompting coastal communities to flee inland, fearing another tsunami.