Police are investigating the motive behind a group's decision to gather outside  Istana Negara with flags and documents while claiming to be heirs of the Yang di-Pertuan Agong.

NONE Kuala Lumpur CID chief Ku Chin Wah said the 12, including two children, were being detained for further investigation.

Ku said the 12 had been arrested for unlawful assembly under Section 121B of the Penal Code, which dealt with "offences against the authority of the Yang di-Pertuan Agong."

"We would like to know what is the motive behind their move and to investigate further, so we need to detain them," Ku told reporters at the city police headquarters.

According to Bernama , the group, which was unarmed and arrived in three vehicles, claimed to be from "Kumpulan Panji Hitam" of the so-called "Timur Empayar Langkasuka Nusantara".

Ku said the children were that of the group’s leader, adding that the oldest detainee was 53 years and the youngest, 11.

All of them are being held at the Travers police station.

Asked to comment on the group's demands, Ku said this was still being investigated.

"Their claim is unbelievable and out of the ordinary... it doesn't make sense," he said. "I find it very funny but people believe him (the leader, who was not identified).”

Ku said that the leader was born in 1973 in Kedah and had a Malaysian identity card, but Ku declined to reveal the person's identity.