A woman has managed to break free after being attacked and forced to the ground during a sexual assault in Brisbane.

A search is under way for a man who forced a woman to the ground and sexually assaulted her on a Brisbane street.

The woman was walking in Hawthorn, in Brisbane’s inner east, around 10pm on Friday when she was attacked.

A man believed to be ages in his early 40s grabbed the victim from behind on Riding Road and forced her onto the ground.

She managed to break free and escape after a struggle, police say.

The man has been described by police as about 188cm tall with an athletic build, and was wearing a dark navy hooded jacked, blue jeans and white sneakers.

He spoke with an accent that may have been South African.

Anyone with information is urged to contact police.