Six teens, aged between 15 and 19, have been arrested following a series of aggravated robberies and fraud offences across Sydney.

The teenagers have been charged over a string of incidents in Ashfield, Clyde, Homebush West, Hurlstone Park, Marrickville, North Strathfield, Enmore and Padstow.

Detective Superintendent Gary Hutchen described the string of incidents as "street level attacks on defenceless people, walking the streets, going about their normal day-to-day business."

In the Enmore robbery, a 64-year-old was left with life-threatening injuries after he was assaulted on February 24. Now in a stable condition, the man is still undergoing treatment.