A convenience store worker was stabbed when a gang of teenagers allegedly attempted to rob the Sydney business.

Police today charged four more teenagers over the alleged stabbing and robbery at  Burwood in the city's south-west about 2.20 am yesterday.

A 28-year-old male staff member who intervened was left hospitalised in critical condition when he was allegedly stabbed by one of the gang.

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He remains in hospital today in a critical but stable condition.

Yesterday at 8am, police patrolling Blacktown railway station arrested a 17-year-old boy. He was then charged with wounding, robbery and other offences.

Later, police arrested two boys, aged 13 and 16, and a 15-year-old girl at the station.

They were charged with rob

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