Vancouver police are searching for a suspect who allegedly groped a 12-year-old girl walking by on the street with two friends in a busy area of Vancouver's downtown.

Police say the incident took place after three young girls left a downtown community centre on Friday night.

As they walked past a 7-Eleven at the intersection of Denman and Comox Streets, they noticed a man staring at them and whispering to another man. When the girls headed west to Chilco Street the man ran up to them, police say.

The stranger "sexually assaulted the 12-year-old by groping her," police said in press release.

He then ran off along Pendrell Street, heading north onto Gilford Street.

"The girl was extremely shaken and upset, but not physically injured," said police.

The man is described as white with some facial hair, wearing grey clothing and a dark coloured hat and black backpack.

Investigators are looking for witnesses and any video that may have captured his image.