SINGAPORE - Posing as a Housing Board officer, a 52-year-old paedophile and career criminal tricked a 16-year-old neighbour to his flat, where he sexually assaulted her and recorded the abuse on his mobile phone.

After her 2½-hour ordeal, the victim was forced at knifepoint to lure her 12-year-old sister to the flat. The younger girl suffered the same brutal abuse after she was made to watch videos of the attack on her sister.

Four hours after she was abducted, the older girl managed to send out a plea for help to her friends. When the police came knocking, their captor, Hussain Samat, dragged the girls to the toilet and locked them in.

But the older girl convinced him to let them go by telling him that they would just tell the police they were playing a prank. Instead she told them about her ordeal and he was arrested.

On Wednesday (Nov 14), Hussain, now 53, pleaded guilty to eight charges - three of aggravated sexual assault by penetration, one of attempted aggravated rape, one of aggravated molestation, one of impersonating a public servant, one of making an obscene film and one of showing an obscene film to a young person.

Another 21 charges - including for abduction, criminal intimidation and causing hurt - will be taken into consideration during sentencing.

Deputy Public Prosecutor David Khoo sought the maximum term of 20 years' preventive detention for Hussain, to protect the public by ensuring that he is "taken out of circulation".

Since 1985, Hussain has been fined, jailed and caned for various offences, including armed robbery, drug possession, theft and causing hurt. In 2001, he was given 14 years' preventive detention and six strokes of the cane for sexual offences against a 15-year-old boy and a 14-year-old girl.

"The accused is clearly a menace to society and is incapable of reform. He is a danger to the public," said the DPP.

The most recent offences took place on May 6 last year, when Hussain hatched a plan to rob his neighbours by impersonating a HDB officer.

When he got to the sisters' flat, he claimed someone had complained that their family had thrown rubbish near the central rubbish chute. The girls' mother denied this.

Hussain returned to his flat and decided to lure one of the girls to have sex with him.

Carrying a file containing documents and a pen, he returned to their flat and told their mother that one of the girls had to follow him to sign a document stating that they did not throw any rubbish. The older sister volunteered to go.

After the girl signed a piece of paper, he beckoned her to follow him to his flat.

Standing outside his open door, he pretended to talk to someone inside, then motioned the girl to pick up a bag from the living room.

The girl went in and realised there was nobody inside only when Hussain locked the door behind them.

Hussain shoved her onto a mat and turned the TV on full volume. He grazed a knife across her face, asking her if she wanted him to slash the left, middle or right side first. He then demanded sex and took off her clothes.

When the girl asked Hussain to use a condom, he gave her an antibiotic pill, lying that it was a birth control pill. She asked him to crush it and tried to escape while he was in the kitchen. But Hussain caught up with her and shouted: "Do you want me to end you now?"

He tried to rape her but did not succeed, and went on to perform other sex acts on her.

He then ordered the victim to phone her younger sister, giving her instructions to go to his flat.

The younger girl complied with his demands after he warned her that he would cut her sister's face if she did not follow the acts in the videos.

The court heard that a psychiatric assessment of the older girl stated that she felt guilty for having called her younger sister to the flat.

Justice Valerie Thean called for a report to assess if Hussain is suitable for preventive detention. The case will be heard again on Dec 17.