A Melbourne high school has been locked down after two students were injured in an alleged affray.

Police are investigating after five people allegedly approached students outside Greenvale Secondary College on Glencairn Drive in Greenvale in Melbourne's north about 3.12pm.

A scuffle broke out and two students sustained minor injuries, police said.

In an email to parents, the school's principal said the college was put into lockdown but assured them students and staff are safe.

The five alleged offenders left the area in a car and have not been located.

Police have described it as a "targeted" incident.

An investigation remains ongoing.

More to come.

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