A 16-year-old boy was injured during a brawl involving up to 30 people, some armed with weapons, in Melbourne's CBD on Friday night.

Police had to use pepper spray to break up the fight on Bourke Street - near the corner of Russell Street - in one of the busiest areas of the city at about 7:30pm.

The teenager was taken to hospital with non-life threatening injuries after the fight, which police believe involved two separate groups of males.