Spanish police have arrested four men suspected of links to Islamic militant cells that planned to blow up the High Court and Real Madrid's Bernabeu soccer stadium.
Interior Minister Jose Antonio Alonso said: "These men were part of a group of people who were forming a cell of radical activists, potentially dangerous to the security of the state.
"One of them has links with the March 11 attacks," the minister said, referring to the Madrid train bombs that killed 191 people and wounded 1,900.
Three of the men, all Algerians, were connected to a Salafist cell dismantled last year in Spain, which in turn had supported a France-based cell's foiled plot to attack the Russian embassy in Paris with a car bomb, the ministry said.
Police also arrested a Spaniard of Moroccan origin whom they accused of contacts with Moroccan Amer Azizi. The ministry said he was wanted for his role in the September 11, 2001, attacks on the United States and in the Madrid train bombings.
Authorities believe militants planned a truck bomb attack on the High Court, the special crimes court that is home to at least nine separate investigations into armed Islamic groups.
The cell, also suspected of seeking to bomb Real Madrid's stadium, was organised largely in prison by inmates who grew ever more radical behind bars, investigators said.