The Queen has sent her condolences to the King of Spain in the wake of the country's two terror attacks.
Her Majesty described events in Barcelona and Cambrils, where 14 people were killed, as "deeply upsetting".
In her message to King Felipe, the Queen said: "It is deeply upsetting when innocent people are put at risk in this way when going about their daily lives.
"Our thoughts and prayers are with those who have lost loved ones and the people who are recovering in hospital."
The Spanish royal, who made a state visit to the UK last month, joined thousands of people in Barcelona for a minute's silence on Friday.
Two men charged with murder and membership of a terror organisation as judge orders a fourth suspect to be freed on bail.
Younes Abouyaaqoub was wearing a fake bomb vest when he was killed in the town of Subirats, about 30 miles west of Barcelona.
The man believed to be responsible for driving a van into pedestrians in Barcelona has been pictured as the death toll rises to 15.