THE family of a boy missing following the terror attack in Barcelona have launched a heartfelt appeal to find him.

Julian Alessandro Cadman was with his mother when they became separated, according to a post by his grandfather on social media.

Tony Cadman posted a photograph of Julian on Facebook, and wrote: "My Grandson, Julian Alessandro Cadman is missing. Please like and share. We have found Jom (my daughter in law) and she is (in a) serious but stable condition in hospital.

"Julian is seven years old and was out with Jom when they were separated, due to the recent terrorist activity. Please share if you have family or friends in Barcelona."

In the photograph, Julian is wearing a jumper with a crest that says Chiddingstone Nursery which is a nursery school in Kent.

Mr Cadman's Facebook profile says he lives in Sydney and is from Gillingham, Dorset.

Speaking after Mr Cadman made a plea for information, Theresa May said UK authorities were "urgently looking into reports" that a child, who has dual British nationality, is missing.

According to the Associated Press, Australia's Foreign Minister Julie Bishop told reporters: "We are concerned for one Australian who remains unaccounted for."