THREE Chinese nationals - two mothers and a daughter - were found dead and another teenage girl was brutally stabbed in a midnight triple murder that shocked residents of Yishun and the China community here.

The other woman and a 17-year-old teenage student were found dead in a corner five-room flat on the sixth floor. A fourth victim, a 14-year-old teenage girl, was badly injured with multiple stab wounds on her body.

She was rushed to Tan Tock Seng Hospital and is still undergoing emergency operation.

Police have arrested a 42-year-old China man, who is believed to be the murder suspect.

He was found in the flat when police broke into it. The man did not resist when police arrested him. Two knives were recovered from the murder scene.

The horror of the multiple murders unfolded at around midnight. But most of the residents in the block slept through it and they only knew about it on Friday morning.

Several residents who were still up late on Thursday heard a shouting match from the 6th floor flat, then a loud thud, followed by piercing shrieks from several screaming women. Then it all went silent.

When they went out of their flats to check, they saw a woman's body lying near the rubbish chute.

She was clad in a floral sleeveless dress and beige panties. She is believed to have fallen from the kitchen window of the sixth floor flat.

Madam Mala, who lives on the fourth floor said she was in her master bedroom when she heard a loud thud. She looked out of the window and saw a body on the ground floor.

With her husband and son, they went down the block to check.

Madam Mala said the dead woman appeared to be plump and in her late 30s or early 40s.

'Moments after the loud thud, I heard several woman shrieking from a flat above. And then silence,' she told The Straits Times on Friday morning.

Another neighbour, who lives on the fifth floor, said her husband was playing computer game in his room when he too heard a loud thud around midnight.

Giving her name only as Mrs Loh, she said the woman had fallen from the kitchen window on the sixth floor.

Mrs Loh, 30, a housewife, said two of the dead victims were mother and daughter.

'The mother is tall, slim and appeared to be in her 30s or 40s. The younger girl looked like a student. She seemed demure,' she added.

Some neighbours also said they heard a quarrel from the occupants in the flat moments before the shocking tragedy.

Police said they received a call at about 12.50 am from a member of the public about a woman's body found at the foot of the block. She was facing down.

She was pronounced dead by paramedics at 1 am.

Police investigators searched the block floor by floor and found a blood-stained padlock on the main door of the sixth floor unit.

They broke down the door with the help of the Singapore Civil Defence Force and found three Chinese women with multiple stab wounds on their bodies. Two of them were pronounced dead at 2 am, while the third was rushed to Tan Tock Seng Hospital.

Inside the unlit flat was the murder suspect.

The Chinese occupants moved into the flat more than a month ago and kept mostly to themselves, said neighbours.

The floor outside the murder scene has been cordoned off. A forensic team is still going through the flat.

Police are treating the three deaths as murder and the fourth as attempted murder.