Indonesian authorities are investigating food poisoning cases involving nearly 700 children in Yogyakarta province this week, after students ate meals prepared under President Prabowo Subianto's key free school meal programme, an official said.

The school meal programme, rolled out in January, was a major election campaign promise from Prabowo, but some 15,000 children have fallen ill as of October 29, data from the non-governmental organisation known locally as JPPI showed.

The JPPI has called for the programme to be suspended.

Improper food storage and late delivery of cooked meals are often to blame for the poisoning, authorities have said.

In the Indonesian region of Gunungkidul in Yogyakarta, some 660 students from two separate schools fell ill from poisoning after eating free school meals, regional head Endah Subekti Kuntariningsih said on her Instagram account on Wednesday.

Dadan Hindayana, chief of the national nutrition agency (BGN) which runs the programme, told Reuters on Thursday that authorities were investigating the Gunungkidul cases and had temporarily closed nearby kitchens.

There are 11,000 kitchens across the sprawling archipelago.

Free meals are expected to reach some 70 million recipients by the end of this year, lower than the government's initial target of 83 million due to a lack of kitchens, Dadan told Reuters earlier this month.

BGN said separately on Wednesday that it had instructed kitchen staff to reduce portions of the food to maintain freshness and avoid poisoning.

On Wednesday, Prabowo formed a team of ministers, including the health minister and the BGN chief, to better supervise the programme, BGN said.

The government has earmarked 171 trillion rupiah ($10.3 billion) for the programme this year, but BGN will only be able to spend 99 trillion rupiah by year-end.