Image copyright AFP Image caption Kim Jong-nam had been critical of the regime

An Indonesian woman held over the killing of North Korean leader Kim Jong-un's half-brother thought she was taking part in a TV prank, police say.

Kim Jong-nam is thought to have been poisoned as he waited to board a flight in Malaysia on Monday.

Two women and a man were arrested over the death.

Indonesia's national police chief said one of the women, named as Siti Aisyah, claimed to have been paid to perform what she thought was a prank.

Image copyright REX/Shutterstock Image caption One suspect wore a shirt with "LOL" - "laugh out loud" - written on it

Police believe a poisonous substance was sprayed into Kim Jong-nam's face.

Tito Karnavian, Indonesia's most senior policeman, said the two women had already performed the prank on other men. It involved convincing them to close their eyes before spraying them with water.

He said his information came from Malaysian officials.

Many questions after airport murder

Kim Jong-nam: North Korean regime's critic in exile

North Korea's history of foreign assassinations and kidnappings

More arrests over airport poisoning

"Such an action was done three or four times and they were given a few dollars for it, and with the last target, Kim Jong-nam, allegedly there were dangerous materials in the sprayer," Mr Karnavian told reporters.

"She was not aware that it was an assassination attempt by alleged foreign agents."

A grainy image broadcast in South Korea and Malaysia showed a woman running in the airport, wearing a white T-shirt with the letters "LOL" written on the front.

Ms Aisyah's family and former neighbours in Indonesia have said they are shocked by her arrest.

Her former father-in-law, Tjia Liang Kiong, told the Associated Press that she moved to Malaysia in 2011 with her then husband to find work after their garment-making business went bust. Hundreds of thousands of Indonesian migrants work in Malaysia, where incomes are much higher.

'Political plot'

North Korea has meanwhile demanded that Malaysia immediately release the body of Kim Jong-nam.

The North Korean ambassador to Malaysia said his country had not consented to the post-mortem already carried out and would categorically reject its findings.

"We strongly urge and demand the Malaysian side not to be entangled with the political plot by the forces hostile to the DPRK [the Democratic People's Republic of Korea] who want to damage the image of our republic - and to release the body immediately without any condition," Ambassador Kang Chol said.

Image copyright AFP Image caption The ambassador's statement was the first official comment from North Korea since the death of Kim Jong-nam, who was not identified by name

Malaysia has said it will not release the body until it receives a DNA sample from Mr Kim's next-of-kin.

South Korea's intelligence agency has accused the country's rivals in the north of assassinating Kim Jong-nam, saying Pyongyang had wanted to kill him for years but that he was being protected by China.

Mr Kim was largely estranged from his family, after being passed over for the North Korean leadership in favour of his youngest half-brother. He spent most of his time overseas in Macau, mainland China and Singapore.

He had spoken out in the past against his family's dynastic control of North Korea and in a 2012 book was quoted as saying he believed his younger half-brother lacked leadership qualities.

But he had said he was not interested in assuming the leadership himself.