Police are hunting for a man who grabbed an 11-year old girl and pulled her to the ground during a terrifying attack in Brisbane's north.

Witnesses have told 9News the offender lunged at the girl and grabbed her by the waist on Francis Road, Lawnton, about 3.20pm on Saturday.

The child was then dragged to the ground on the busy overpass, before onlookers confronted the attacker and he fled.

The brazen assault unfolded in broad daylight. (Nine)

“The man tackled her to the ground without warning, and as a result passers-by have started shouting at him,” Joe Zitny from Queensland Police said.

Thanks to the quick-thinking onlookers, the offender fled – driving off in a dark SUV, believed to be a Holden Captiva.

“I heard a car scream … it was going a million miles an hour,” witness Rebecca Bowles said.

Mr Zitny said the victim was distraught in the moments after the brazen assault, but is now in “okay spirits”.

The offender fled in this Holden Captiva. (Supplied)

Investigators spent today door knocking in their search for the offender, who is described as Caucasian in appearance, between 20 to 25 years old and of medium build, with a shaved head and tanned skin.

He was wearing a black singlet, fawn-coloured pants and a chain at the time of the assault.