Boy grabbed in Sydney's northwest

A nine-year-old boy jogging with friends in Sydney's northwest has been assaulted by a man who emerged from bushes, police say.

They say the boy was jogging in Eastwood about 4pm (AEDT) on Saturday when he fell behind his friends and the man grabbed him around the neck and shoulder.

"A short struggle ensued before the boy was able to escape and inform his friend's father of the incident," police said in a statement.

The boy was not injured.

The offender is described as being of Caucasian appearance, aged in his late 30s to early 40s, of average height with a thin build, light brown hair cut in a flat top style, and a small goatee.

He was last seen wearing a white round neck T-shirt and black three-quarter length pants.

Anyone with information is urged to contact police.