Warning - graphic content. A video from the scene of the Barcelona attack shows the horrific aftermath.
By Ellen Whinnett in Spain, Ashleigh Gleeson
A NSW father is travelling to Spain to desperately try to find his 7-year-old son who is missing in Barcelona, while his mother remains in hospital following the horror terror attack.
Julian Cadman is missing while his mother Jom is in a serious but stable condition in hospital after a white van ploughed into crowds on Las Ramblas.
Julian's aunt Hayley has posted a desperate appeal online to help find her nephew.
"My nephew Julian Cadman is missing. Please like and share. We have found Jom and she is serious but stable in hospital," she said.
"Julian is 7 years old and was out with Jom and they were separated. Please share if you have family or friends in Barcelona."
Another friend Megan Cameron posted online: "You never know who it may reach over there and anything we can do to help in the effort to locate him and reunite him with his Mum in hospital".
She said that Andrew was flying to Barcelona tonight to be with his wife and to help find Julian.
he family of Julian Alessandro Cadman have put a call-out on Facebook in the hope of tracking the seven-year-old boy down.
He was in Barcelona with his mother Jom Cadman, when they got separated.
Injured are helped on a long stretch of pedestrian sidewalk after a white van jumped the sidewalk. Photo / AP
His grandfather, Tony Cadman, has posted this message on his Facebook page:
"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."
"My nephew Julian Cadman is missing. Please like and share. We have found Jom and she is serious but stable in hospital," Claire O'Sullivan wrote on Facebook.
"Julian is 7 years old and was out with Jom and they were separated. Please share if you have family or friends in Barcelona."
News Corp Australia has contacted DFAT for a response on the status of the boy and his mother.
Injured are helped after the attack. Photo / AP
Foreign Minister Julie Bishop said a total of eight Australians were caught up in the incident when a van ploughed into crowds on the famed Las Ramblas tourist street, which left at least 13 dead and more than 100 injured.
It was one of two attacks to rock Spain, with a second incident involving a van ending with five terrorists being shot dead by police.
Armed police officers patrol a street in Las Ramblas, Barcelona, today. Photo / AP
Of the eight Australians impacted by events in Barcelona, Ms Bishop said four were injured, three required consular support and one is unaccounted for.
"Of the four injured, that includes one woman, who is from New South Wales in a stable condition, but was seriously injured," she told media. "A second woman, also from New South Wales, is in a serious condition in hospital."
In the Cambrils incident, suspects wearing suicide belts were shot dead by police in Cambrils after ramming into a crowd.
Police were pursuing a suspicious van that then drove into a pedestrian area on an esplanade, running down six people before the vehicle overturned. A police shootout then followed, with five attackers killed.
Firearms were removed from the scene and belts they were carrying are being treated as potential explosive devices.
Reports suggest that the group of terrorists in Cambrils tried to re-create the earlier attack in Barcelona, which came mid afternoon Spanish time and also left at least 100 people injured them, Catalan police confirmed. Fifteen of them are in a critical condition.
Local media is reporting Spanish police are following up from both incidents with a series of raids in the region surrounding the district centre of Terragona.
Police earlier warned local residents and tourists at nearby hotels to stay indoors: "If you're now in Cambrils, avoid going out. Stay home, stay safe," the region's civil defence agency said in a tweet.
It has since tweeted that the situation "is under control", though it advised people in the area to remain "cautious".
Two men - a Spanish national and a Moroccan - have been arrested in relation to the attack but police said the driver of the van was still on the run.
Islamic State has claimed responsibility for the terror attack, according to the Amaq news agency.
After the van attack in Barcelona, authorities said a Belgian was among the dead and a Greek woman was among the injured.
Germany's Foreign Ministry said it was checking reports that German citizens were among the victims.
At least one Australian from NSW is reported to be in a serious condition.
Foreign Minister Julie Bishop said two Victorians were waiting to seek medical attention for minor injuries, and the total number killed in the incident was 16. This death toll is yet to be confirmed.
There were scenes of panic on the famous thoroughfare, with bodies strewn in the street.
Eyewitnesses said the van was travelling at speeds of up to 80km/h when it mounted the footpath, and then zigzagged down the Las Ramblas promenade for up to 500m before it came to rest with a badly injured person crumpled near the front wheels.
Terrified tourists were seen fleeing as the van smashed its way through street furniture and pedestrians, in an attack chillingly similar to those in London this year, and in Nice in southern France a year ago.
Islamic State has claimed responsibility for the terror attack, according to the Amaq news agency.
Twitter images of what is believed to be the white van used in the terror attack at Las Ramblas. Photo / Supplied
TERROR ARRESTS
Following the attack, Spanish police distributed an image of Driss Oukabir, whose ID had been found in a second rental van believed to be the getaway vehicle.
The 28-year-old Catalan resident of Moroccan origin later handed himself in to police in Ripoll, about 100km from Barcelona.
Oukabir claimed that his younger brother, Moussa Oukabir, 18, had stolen his documents.
The second person arrested was a Spanish national born in the Spanish territory of Melilla in northern Morocco.
"It was clearly a terror attack, intended to kill as many people as possible," Josep Lluis Trapero, a senior police official, told a news conference this morning.
The arrests took place in the northern Catalan town of Ripoll, and in Alcanar, some 200 kilometres south of Barcelona, the site of a gas explosion at a house earlier in the week which was initially thought to be drug related.
Police now suspect the explosion is linked to the van attack.
Trapero said the explosion left at least one person dead, and police suspected those in the house were "preparing an explosive device."
"It seems there was an accumulation of gas that generated the explosion," he said, without giving further details.
The town of Cambrils, the site of an ongoing police operation, on the coastal road between Barcelona and Alcanar.
The area around Barcelona's Las Ramblas was sealed off for blocks in each direction, and tourists and locals were desperately trying to find loved ones, as the mobile phone network in the area struggled to cope.
Islamic State's Amaq news agency published a statement saying: "The perpetrators of the Barcelona attack are soldiers of the Islamic State and carried out the operation in response to calls for targeting coalition states" - a reference to a US-led coalition against the Sunni militant group.
