Many children were killed in an earthquake in Indonesia when their schools collapsed, officials said on Tuesday, as rescuers raced to reach people trapped in rubble in a devastated town on Java island.

Hundreds of people were injured in the Monday quake and officials warned the death toll was likely to rise.

The shallow 5.6-magnitude quake struck in mountains in Indonesia's most populous province of West Java, causing significant damage to the town of Cianjur and burying at least one village under a landslide.

Landslides and rough terrain were hampering rescue efforts, said Henri Alfiandi, head of National Search and Rescue Agency (Basarnas).

"The challenge is the affected area is spread out ... On top of that, the roads in these villages are damaged," Alfiandi told a news conference, adding that more than 13,000 people had been evacuated.

"Most of the casualties are children, because at 1 pm they were still at school," he said, referring to the time the quake hit.

President Joko Widodo traveled to Cianjur on Tuesday to encourage rescuers.

"My instruction is to prioritize evacuating victims that are still trapped under rubble," said the president.

While strong earthquakes of magnitude 6 or 7 are relatively common in Indonesia, often offshore where fault lines run, Monday's quake of a lower magnitude had such deadly consequences because it struck on land at a relatively shallow depth.

Officials said many of the dead were killed when poorly constructed buildings collapsed with the president calling for reconstruction efforts to include earthquake-proof housing.

Survivors gathered overnight in a Cianjur hospital parking lot. Some of the injured were treated in tents, others were hooked up to intravenous drips on the pavement as medical workers stitched up patients under torchlight.

"Everything collapsed beneath me and I was crushed beneath this child," Cucu, a 48-year-old resident, told Reuters.

"Two of my kids survived, I dug them up ... Two others I brought here, and one is still missing," she said through tears.

"Many dead bodies are lying in the hospital grounds, it's very crowded," said her relative, Hesti.

Footage from Kompas TV showed people holding cardboard signs asking for food and shelter, with emergency supplies seemingly yet to reach them.

Hundreds of police officers were deployed to help the rescue effort, Dedi Prasetyo, national police spokesperson told the Antara state news agency.

"Today's main task order for personnel is to focus on evacuating victims," he said.

(Cover: Evacuating a victim of a landslide due to an earthquake in Cugenang Village of Cianjur, West Java, Indonesia, November 22, 2022. /CFP)