UK stands with Spain against 'evil' terrorism: PM May

London: The UK stands with Spain following the "appalling" twin terror attacks in which at least 14 people were killed and 80 others injured, British Prime Minister Theresa May said on Friday.

A van ran into a crowd of pedestrians walking through Barcelona's famed Las Ramblas area yesterday, killing at least 13 people and wounding many others, including some British nationals.

Police later shot dead five suspects after a second vehicle attack in the coastal town of Cambrils, around 130- kilometre from Barcelona.

Officials in Barcelona said today the death toll in the attack in the heart of the city has gone up to 14.

"The UK stands with Spain against terror. 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," May said.

"Following the attacks in Manchester and London, Spain stood alongside the British people. Tonight, Britain stands with Spain against the evil of terrorism," she said in a statement.

The Spanish flag and the UK's Union Jack are flying at half-mast at Downing Street in London and other government buildings in the UK.

The UK Foreign Office has said that a "small number" of British nationals were injured in the attacks in Spain.

"Our thoughts are with the victims of these terrible attacks and the people of Spain," a spokesperson said.

"We are currently assisting a small number of British people affected and are working to find out if any more need our help. We have deployed additional staff to Barcelona and have offered support to the Spanish authorities," the spokesperson said.

The Foreign Office has also issued advised British tourists in Spain to take care and follow the advice of local security authorities.

"Concerned and saddened by #Barcelona attack. Our thoughts are with those affected. Doing all we can to identify whether Brits need help," UK foreign secretary Boris Johnson said on Twitter.

"Terrible reports from Barcelona. My thoughts are with those killed and injured, and the emergency services working to save lives," Opposition Labour leader Jeremy Corbyn tweeted.

"London stands with Barcelona against the evil of terrorism," said London mayor Sadiq Khan in his message.

Spanish investigators believe a 12-strong terror cell is behind the two attacks, which was originally planning a deadlier attack involving gas canisters.

They are working on the theory that the attacks in Cambrils and Barcelona are linked to a gas explosion at a house in the town of Alcanar on Wednesday that killed one person.