Meanwhile, a Spanish TV station broadcast previously unseen security-camera footage of the March 11 train bombings at Madrid's Atocha rail station. It shows an orange fireball bursting from a train, engulfing commuters with smoke and leaving the platform littered with bodies and stained with blood.
Seven suspects were arrested on Monday in Madrid and southern Spain, and one more Tuesday in the northern city of Pamplona. Most are Algerian, and some had contacts with militants elsewhere in Europe, the United States and Australia.
"This was an operation against radical Muslims. They were planning to commit terrorist attacks," Interior Minister Jose Antonio Alonso told reporters at Parliament.
"They were talking about attacking the National Court, a judicial body. But the police do not rule out any other kind of possibility," Alonso said, adding that no explosives were found during the arrests.
The leader of the cell, Mohamed Achraf, was born in the United Arab Emirates and was arrested over the past few days in Switzerland, a Spanish police official close to the investigation said.
The newspaper El Pais quoted police sources as saying the alleged plot against the court was in the preliminary stages as there was no evidence that the suspects had obtained explosives.
Another newspaper, El Mundo, reported that the plan involved detonating a truck loaded with 1,100 pounds of explosives outside the courthouse, located on a busy avenue in downtown Madrid.
The Spanish police official denied reports in El Mundo that the cell had tried to obtain explosives through the Basque separatist group ETA. Instead, he said, the cell had dealt recently with a Spanish man of Gypsy ethnicity.
Swiss police made the arrest on a request from Judge Baltasar Garzon of the National Court. The arrests in Spain were also ordered as part of a probe by Garzon, Spain's leading anti-terrorism magistrate.
Since September 2003, Garzon has indicted 41 people on terrorism charges, including Osama bin Laden and other al Qaeda suspects accused of staging the Sept. 11 attacks in the United States.
The Algerian suspect arrested Tuesday in Pamplona, named as Majad Sahouane, is close to Imad Yarkas, the suspected leader of a Spanish al Qaeda cell at the center of that indictment and charged with providing financing and logistics for Sept. 11 plotters, according to Jean-Charles Brisard, a French private investigator working for lawyers representing Sept. 11 victims.
Brisard has access to Garzon's case file, which is thousands of pages long. He said Garzon ordered Sahaoune's phone tapped in Spain in November 2001. But there is no evidence that Sahouane was implicated in Sept. 11, Brisard said in an interview from Paris.
Another judge at the National Court, Juan del Olmo, is leading a probe into the March 11 train bombings in Madrid, which killed 191 people and have been blamed on Muslim militants linked to al Qaeda.
Spanish TV station Telecinco Tuesday broadcast chilling security-camera footage of the Madrid attack, including at least one bomb exploding inside a train at Atocha.
The Telecinco footage was believed to mark the first public broadcast of actual video images of the March 11 attacks.
The video footage starts with dazed commuters milling about on a smoke-shrouded platform after one explosion. The time on the security camera said 7:38 a.m.
Then, smoke flows toward the camera and people on the platform are apparently knocked over by another blast.
About five seconds later, a ball of orange flame erupts from a stopped train, filling the screen. The tape includes no sound, just images.
The footage appeared to have been taken from atop an escalator, looking down onto the platform.
Four minutes later, bodies are seen strewn on the platform amid puddles of blood. Police and emergency medical staffers attend to them.
After another five minutes, police and crews are seen screaming for people to evacuate the station and themselves running toward the escalator, fearing another explosion. Telecinco said this warning turned out to be a false alarm.
Telecinco also aired two other pieces of March 11 video that had not been broadcast publicly, although their existence was known.
One shows a gun-carrying, masked militant claiming responsibility for the attacks on behalf of al Qaeda. The video was found near a mosque on the eve of Spain's March 14 general election.
"We claim responsibility for the Madrid attacks, two and half years after the blessed conquests of New York and Washington," the Arabic-speaking man said, according to Telecinco's translation. He was referring to Sept. 11.
In the other video, made on March 27, three hooded men wearing belts loaded with dynamite cartridges threaten more attacks against Spain unless it withdraws its troops from Afghanistan.
Those three are now believed to have been ringleaders of the March 11 bombing cell and among seven suspects who blew themselves up in an apartment outside Madrid on April 3 as police prepared to storm it.
The original video was found among the rubble of the apartment. The government had said it was badly damaged, and reconstructed it.