A seven-year-old Australian boy is feared missing after the Barcelona terror attack at Las Ramblas, killing more than a dozen people Friday.
Julian Cadman remains unaccounted for after a van plowed into pedestrians killing at least 13 -- and according to Malcolm Turnbull up to 16 -- and injuring up to 100 people.
Family and friends are sharing his image on social media.
The Sydney boy is said to have been separated from his mother, who was injured in the attack and reportedly remains in a serious condition at Barcelona hospital.
A long-term friend of young boy's family, known only as Scott, told 2GB radio host Ben Fordham Julian's father first heard about the devastating news of the attack when he arrived at work on Friday morning and was unable to get into contact with his wife.
"He turned up to work this morning, turned the news on this morning at 6 o'clock, heard about it, tried to ring his Mrs [sic], couldn't get hold of her," he said.
"By about 8:30am, we found out that it was her in the hospital, she's in a very serious condition [and] he's on his way to the airport.
"We found out an hour later this his seven-year-old son was with her. He's missing and we haven't heard anything since. We don't know if he's still with us or not."
Another woman, also from NSW, was seriously injured but is now in a stable condition.
It is understood two men from Victoria were hit by the car and injured, and both have since been discharged from hospital.
Earlier Foreign Minister Julie Bishop confirmed four Australians were among injured in Friday's attack on the popular tourist spot. Australia is liaising with authorities to find the Australian who is unaccounted for.
She said she was "concerned" for the unaccounted for Australian.
The attack was the deadliest in Spain since 2004, when al Qaeda-inspired militants detonated bombs on Madrid's subway system, killing 191 and injuring more than 1,800.
Just hours after the Barcelona attack, police said they killed five people in response to a separate terrorist plot in the southern coastal town of Cambrils, about 100 kilometres southwest of Barcelona.