A major crime scene has been declared outside of a massive comic convention in Melbourne, after reports a car drove through a crowd of people.

Emergency services were called to the corner of Langs Road and Epsom Road in Ascot Vale, outside of the Melbourne Showgrounds, just after 5pm.

The venue was hosting the Supanova Comic Con, where thousands of people are believed to have been present.

Witnesses told 9News they saw a car driving "at speed" towards a group of people, and it has been described as a "chaotic situation" at the scene.

Victoria Police has been contacted for comment.

More to come.