A huge explosion at a house 120 miles south of Barcelona on Wednesday night is now being linked by police to the terrorist attack a day later.

Police in Spain initially dismissed the explosion in Alcanar as a gas explosion.

But on Thursday night, hours after the attack that killed at least 13 people and wounded 100, they revised their initial response.

Josep Lluis Trapero, head of the Mossos police, announced at a press conference that they now believe there is some connection between the occupants of the house and the perpetrators of the Barcelona attack.

At least one person was killed and six injured when the house blew up, causing substantial devastation to nearby buildings. The sound of the explosion was heard several miles away, according to locals.

Inside the house, which police believe was occupied for a few months, they found around 20 canisters of butane and propane gas.

A woman was found dead and a man, discovered among the rubble, was taken to hospital in a critical condition.

The other injured people are thought to be neighbours.

"I was having dinner with some friends when we felt a massive boom - the lights went out and the windows shattered," said Elliane Fernandez, a Frenchwoman who lived nearby.

"I called out for my husband, who was injured in the head and taken to hospital, and a cousin was also injured.

"The rest had cuts, light injuries."

She told El Pais that she did not know the neighbours, living in the house that exploded.

Alfons Montserrat, mayor of Alcanar, said they did not yet know whether the house was being legally rented.

He said that some of the neighbours had been given temporary housing, after the explosion.