A grandfather has made an emotional appeal for information about his seven-year-old grandson missing in yesterday's Barcelona attack.
Young Julian Cadman was separated from his mother, Jom, after a van ploughed into crowds on Las Ramblas.
She is in a hospital where she is in a serious but stable condition.
It is being reported the boy is a British national.
The British Prime Minister, Theresa May, said UK authorities were "urgently looking into reports" that the child, who has dual British nationality, is missing.
Grandfather Tony Cadman whose Facebook profile says he lives in Sydney and is from Gillingham, Dorset, England, posted a Facebook message: "My Grandson, Julian Alessandro Cadman is missing. Please like and share.
"We have found Jom (my daughter in law) and she is serious but stable condition in hospital.
"Julian is 7 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."
If you can't see the Facebook post above, click here.
Julian's father Andrew is on his way to Spain from Sydney to search for his missing son.
Julian’s aunt Hayley also posted a Facebook message appealing for information on her nephew.
She said: “My nephew Julian Cadman is missing. Please like and share. We have found Jom and she is serious but stable in hospital.
“Julian is 7 years old and was out with Jom and they were separated. Please share if you have family or friends in Barcelona.”
The British Prime Minister said: "The UK stands shoulder to shoulder with Spain in confronting and dealing with the evil of terrorism, and I have offered any assistance we can provide.
"Sadly I must tell you that we do believe that a number of British nationals were caught up in the attack and we are urgently looking into reports of a child believed missing, who is a British dual national."