The Interior Ministry had raised the terror alert after multiple attacks in other countries on June 26th, but Spanish media reported on Monday that the alert will remain high due to mentions of Spain within jihadist groups.
The June 26th attacks, known as "Bloody Friday" or "Black Friday", took place across three continents, in France, Tunisia, Kuwait and Somalia. The one in Tunisia left 38 people dead at a Spanish hotel.
Newspaper El País reported that there has been a sharp increase in the number of messages about Spain within terrorist networks linked to Isis, but that the government has not detected a concrete threat planned on Spanish soil.
"But we must be very vigilant and on alert because there are people with the capacity to launch and execute an attack at any time," anti-terrorism sources said.
Officials said that there are generally two types of messages: those that directly threaten Spain and those that seek to recruit jihadists.
Not only have mentions of the country increased, but the level of violence within the messages has also increased, sources told El Pais.
The terror level will be set for at least this week at a level four, meaning 'high risk', with five being the highest. Spain has not been at such high alert since the 2004 Madrid bombings by Al-Qaeda inspired radicals, which left 191 dead and about 2,000 injured.
The increased alert will mean more police presence on the streets of cities as well as at airports, railway and bus terminals, nuclear power plants and electrical installations.
With the spread of Isis in recent years, the Spanish government has been cracking down on jihadist networks throughout the country. On Tuesday, national police arrested a woman in Lanzarote in the Canary Islands for recruiting young girls to join Isis fighters. The Spanish woman reportedly had direct connections to operatives in Syria.
More than 40 people have been arrested so far this year for their involvement with Isis, mostly by recruiting others to join fighters abroad.
About 116 people have left Spain to fight for Isis in Syria and Iraq, which is still a low number compared to countries like France, Germany or the United Kingdom which have each seen multiple hundreds of people leave to join radical groups.