Sydney man critical after robbery stabbing

A 29-year-old man is in critical condition after he was stabbed in the back and stomach during a robbery and altercation in Sydney's west.

A man is in critical condition after being stabbed during a robbery in Sydney's west.

Police were told men, aged 29 and 30, went to Flemington Railway Station in Homebush West on Sunday night to buy two mobile phones that were advertised online.

The two men who met the pair snatched their money and fled. The younger chased them down and argued with them before he was stabbed in his back and stomach.

Police are appealing for information and witnesses.