Spain is deploying more than 40,000 police officers to guard tourist hotspots and other sites across the country this summer amid fears of terror attacks.
British holidaymakers will notice extra security at destinations such as Ibiza, Majorca, the Canary Islands and the capital Madrid from July 1.
Officers from the National Police and Civil Guard will be stationed at airports, train stations, landmarks, festivals and beaches until the end of August in most places as part of the anti-terror Operation Summer.
Britain's Foreign Office has warned holidaymakers that terror attacks are "likely" and they should be vigilant and follow the instructions of local authorities.
The plan by Spain's Interior Ministry includes "strengthening actions to obtain information on the prevention of terrorist acts", with special attention to the threat of jihadist terrorism, according to reports.
Extra security will be deployed to events or places where there will be huge crowds, and there will be additional surveillance.
Operation Summer will run from July 1 to August 31 in Andalusia, Asturias, the Canary Islands, Cantabria, Galicia, Madrid, Murcia and Valencia.
It will run until the end of September in the Balearic Islands, including Ibiza and Majorca.
The reports did not identify any specific threats.
Last week, a group aligned with ISIS published a propaganda poster depicting a jihadist outside Gaudi's unfinished La Sagrada Familia in Barcelona.
ISIS' propaganda machine has threatened Spain three times recently.
Spain's national terror alert level remains unchanged.
The alert level has been at four or "high" - one below the maximum level, five or "very high" - since June 2015.
It was raised following terror attacks in France and Tunisia that year, and it has remained at four since the terror attacks in Barcelona in August 2017.
It was last at level one - the lowest on the five-level scale - in 2009.
What is the Foreign Office's advice?
In its travel advice for British holidaymakers, the Foreign Office says: "Terrorists are likely to try to carry out attacks in Spain.
"Attacks could be indiscriminate, including in places visited by foreigners.
"The Spanish authorities take measures to protect visitors, but you should be vigilant and follow the instructions of the local authorities."
It adds: "Spanish police have disrupted a number of groups suspected of recruiting individuals to travel to Syria and Iraq from 2015 to the present date.
"Some of them expressed an intention to carry out attacks in Europe.
"There’s a heightened threat of terrorist attack globally against UK interests and British nationals from groups or individuals motivated by the conflict in Iraq and Syria.
"You should be vigilant at this time."
