Two knife-wielding teenagers are facing charges after a brazen daylight crime spree in Melbourne’s CBD, which was brought to an end with the help of heroic bystanders.

The two teens, aged 16 and 17, are accused of launching their rampage near Southern Cross Station about 8.30am on Thursday, where they allegedly punched a man in the face while trying to steal his scooter.

WATCH THE VIDEO ABOVE: Bystanders stop crime rampage by teen on bail.

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They fled empty-handed but soon targeted another man on Bourke Street Bridge, allegedly demanding his vape and threatening to stab him.

When he refused, police say they followed and assaulted him.

Their third victim was approached on St Kilda Rd, where the pair allegedly demanded his headphones before hitting him in the eye.

All three victims suffered minor injuries but didn’t require hospital treatment.

With the help of bystanders, police arrested one teenager on the corner of Elizabeth and La Trobe streets, and the other nearby on Lonsdale St.

One of the boys allegedly assaulted a police officer during the arrest, damaged a police CCTV camera, and assaulted two officers back at the station.

7NEWS understands the 17-year-old Kinglake boy was released on bail just eight days earlier but breached all three bail conditions.

He has been charged with attempted armed robbery, attempted theft, unlawful assault, and resisting police.

He was remanded in custody to appear at a children’s court at a later date.

The 16-year-old from Doreen faces charges including attempted armed robbery, attempted theft, unlawful assault, resisting police, possession of a controlled weapon, and assaulting police.

He was granted bail to appear at a children’s court at a later date.