SINGAPORE - A father fed up of his son's rudeness took a chopper and slashed him and his girlfriend after an argument.

Weng Kim Song, 74, left 33-year-old Mr Benson Yuan Pei Sheng with a broken left wrist and forearm as well as gaping wounds, afterhe hurled vulgarities at his fatherin a phone call.

The retiree was jailed for three and a half years on Tuesday (July 3) after pleading guilty to causing grievous hurt with a weapon.

A second assault charge involving Mr Yuan's girlfriend, Ms Calinda Yeo Hui Ping, 27, was considered during sentencing, although her injuries were not revealed in court documents.

The incident was sparked on March 25 after Weng called his wife's mobile phone and it was answered by Mr Yuan,who was rude to him.

The pair argued before the father hung up. That evening back at their Commonwealth Close flat, he spotted his son and his girlfriend asleep in a bedroom.

He decided to confront Mr Yuan about his rude attitude and grabbed the chopper - which had a 22cm blade - from the kitchen.

Deputy Public Prosecutor Houston Johannus said: "The accused's intention of arming himself with the chopper was to slash the victim with it if he did not apologise."

Mr Yuan was angry to see his father in his room when he woke up and the pair quarrelled again before Weng attacked his son. Ms Yeo was slashed when she tried to stop the attack by throwing a bolster at Weng.

Weng's 70-year-old wife Madam Ho Bee Choo rushed into her son's room when she heard the commotion and took the weapon away from her husband.

She threw the chopper out of a window of the sixth-storey flat and a passer-by alerted the police after Weng was spotted retrieving it from the ground floor.

Officers arrested him in his flat later that evening and the injured couple were taken to hospital.

DPP Johannus urged District Judge Kessler Soh to jail Weng for four years as he had caused serious injuries to his son.

Weng's lawyer, Mr Christopher Sim, who was assigned to the case under the Criminal Legal Aid Scheme, pleaded for a jail term of three years or less. He also said that Mr Yuan is now living with a cousin and has since forgiven his father.

Court papers did not state why the father and son have different surnames.