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, about 10am on Tuesday.

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

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

The other two victims were transported to hospital in a critical condition.

Police have not formally identified the dead individual and did not provide identifying information regarding any of the victims.

Shortly before 11am, police said a man had been arrested and taken to the nearby Granville Police Station.

The man was arrested on Smythe St in Merrylands.