TOKYO - JAPANESE police arrested a woman believed to be a devoted mother for allegedly trying to murder her toddler daughter by injecting her with rotten water in hospital, an official said on Thursday.

The woman, 35, whose name was withheld for the sake of the surviving girl, was arrested Wednesday in the western city of Kyoto on suspicion of attempted murder, a police spokesman said.

Police said the girl was the youngest of the woman's five daughters.

Reports said three of them had died before they turned four due to illness.

The mother denied the intention to kill, while admitting she made 'rotten water' by letting a mixture of a sports drink and water go bad, police said.

'I didn't do that to kill her. I thought I could continue to take care of her if she gets sick,' she told investigators, as quoted by police.

Local media said the woman may have a mental disorder known as Munchausen Syndrome By Proxy, whose sufferers may intentionally sicken their children so they can perform the role of devoted parents.

A hospital camera caught her injecting her 22-month-old daughter with the contaminated water through an intravenous drip, the police spokesman said.

The girl was in an intensive care unit of a Kyoto hospital for blood poisoning.

The woman seemed to be taking good care of her sick daughter, with a relative quoted on television as saying she was a devoted mother.

But suspicion grew at the Kyoto University Hospital as the girl repeatedly had a high fever after the mother acted strangely around her.

'She was excessively hugging her and was interested in the IV but I presumed it was because of her strong maternal instincts,' hospital deputy chief Satoshi Ichiyama told reporters late Wednesday.