A teenager, 17, punched his mother, stabbed his stepfather and slashed a policeman after his mum refused to give him money to buy a new handphone.

According to Lianhe Wanbao, the incident happened at Yishun Ring Road at about noon yesterday.

The mother, 41, told Wanbao that her son asked her for $1,000 two days ago to buy a new handphone but she refused. Yesterday, she saw him slip into his uncle's room to steal his handphone and about $100 in cash.

His mother reprimanded him, but he only asked her for money again.

"I gave him some money, but he kept saying it wasn't enough. I was so angry that I scolded him fiercely," she said.

Angered by her reprimands, he punched her in the face, prompting her to call the police.

Three policemen arrived and were taking his statement outside their flat when his stepfather returned from work. When he learnt that the teen had punched his mother, he gave him another scolding and two tight slaps. He then turned to step into their house.

The resentful teen blew up again, drew out a knife and attempted to stab his stepfather. One of the policemen stretched out his hand to block him and was slashed on the wrist.

On his second attempt, he stabbed his stepfather in the back, on his left shoulder.

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The teen will be charged in court tomorrow, but his mother has refused to post bail.

She says "My son is very rebellious, he has been expelled from school. He cannot hold any job for long, and asks me for money every few days.

"I've known my husband for more than 10 years, but we just registered our marriage this year. He is a good father, and it breaks my heart to see my son hurt him like this.

"I'm not going to bail him out this time, I hope he learns his lesson."

Names and addresses have been withheld to protect the family's identity.