The police said that the attackers were wearing explosive belts.

At least 13 people were killed and about 50 wounded when a van ploughed into a crowd in Barcelona's tourist area of Las Ramblas on Thursday.

The incident has been described as a 'jihadist attack' by Spain's Prime Minister Mariano Rajoy.

Spanish authorities have also linked the attacks with an earlier incident in the town of Alcanar that left one person dead.

Earlier, police chief Josep Lluis Trapero was quoted in the media as saying that the residents in the Alcanar building was making an explosive device.

Meawhile, SITE Intel Group tweeted that Islamic State has claimed responsibility for the attack according to Amaq News Agency of the IS.

Following the attack, world leaders have took to social media to condemn the incident and condole the loss.

"The United States condemns the terror attack in Barcelona, Spain, and will do whatever is necessary to help. Be tough & strong, we love you!" US President Donald Trump tweeted.

Former American President Barack Obama's tweet read, "Michelle and I are thinking of the victims and their families in Barcelona. Americans will always stand with our Spanish friends. Un abrazo."

British Prime Minister Theresa May said in an official statement, "I am sickened by the senseless loss of life in Barcelona today. The Foreign Office is working to establish if any British nationals were involved in this appalling incident and we are in close contact with the authorities in Spain, who have our full support."

"Following the attacks in Manchester and London, Spain stood alongside the British people. Tonight, Britain stands with Spain against the evil of terrorism," May's statement read.

Canada's Prime Minister Justin trudeau said, "Canada condemns today’s terror attack in Barcelona – our hearts, sympathies & support are with the victims and their families."

Image: Screengrab from BBC