A six-year-old boy, a foreign national, and his grandmother, 80, were killed in their home in Felcra Batu 9, Teluk Panglima Garang, early Sunday morning.

Selangor police chief, Datuk Abdul Samah Mat said in the incident at about 3am, a man, believed to be known to the family, went to the home of the victims in Jalan Rumbia, Sijangkang, where he said he was taking the boy and his older sister, 11, to meet their mother.

"The suspect, aged 31, then brought the three to an oil palm plantation. When they arrived at a certain spot, the suspect dropped the grandmother and continued on with the two children.

"Not far from there, the children were let down, and the suspect tried to rape the girl, but did not succeed as the boy screamed for help.

"The suspect then beat the boy with a stick until he died," Abdul Samah said at a press conference, Monday.

Seeing what happened, the girl escaped and went to a house near the plantation to ask for help.

"The occupants of the house then contacted the police and when the police arrived at the scene of the incident, they found the boy's body in a drain," he said.

Based on information from the girl, police traced the suspect and arrested him at a petrol station along the Shah Alam Highway (Kesas) at about 5am Monday and then went to his house to detain his wife.

"Following the questioning of the suspect, police returned to the location of the incident and found the body of the grandmother about 100 metres from where the boy was found.

"The two bodies had injury marks caused by being hit by a hard object," he said, adding that the motive of the murders were being investigated.