A man is in custody after three people were stabbed near a train station in western Sydney, leaving one of them dead.

Police responded to reports of the stabbing in Merrylands at about 10am on Tuesday.

They were told a man had fled on foot after stabbing multiple people.

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Paramedics treated the three victims at the scene, with one declared dead.

The other two victims – a man aged 22 and woman aged 47 – were transported to hospital in a critical condition.

Merrylands Road, where three people were stabbed on Tuesday, one fatally. Photograph: Bianca de Marchi/AAP

Police had not formally identified the dead man, but said on Tuesday afternoon that he was aged between 30 and 40 years old.

Shortly before 11am, police said a man had been arrested on Smythe Street in Merrylands and taken to the nearby Granville police station.

Supt Simon Glasser said the crime scene spanned 50 metres along Merrylands Road. It remained cordoned off at 1.30pm.

Glasser said there was no known relationship between the three victims and the attacker. The victims were “by themselves on Merrylands Road,” he said, confirming two of the attacks occurred inside a premises, and one was on the street.

“Police are unaware at this point what the motive was,” he said. “It’s a horrible offence to have taken place in Merrylands just prior to lunchtime with lots of people around.”

The superintendent said it was a “confronting scene”, but it was “very reassuring to see members of the community come and help” the injured.

Glasser said the alleged offender had no links to the address where he was arrested. He was known to police for “petty crime and a number of mental health incidents”.

Police recovered a 20 to 30cm kitchen knife after the arrest, but it was unclear if it was the same weapon used in the attacks, Glasser said.

A shop assistant in the cordoned-off part of Merrylands Road, who did not wish to be identified, said she heard a commotion after the nearby stabbing.

“It’s very bad,” she said.

Glasser said the alleged offender would probably face court on Tuesday afternoon.

NSW police at the scene in Merrylands in western Sydney. Photograph: Bianca de Marchi/AAP