(CNSNews.com) - Thirteen members of Islamic terrorist groups were rounded-up Monday morning in Paris and held on suspicion of belonging to the Moroccan Islamic Combatant Group, which has been accused of carrying out the Casablanca bombings in May 2003.

This same group is also under suspicion of ties to the March bomb attacks in Madrid that killed 191 people.

A judicial police source confirmed the detentions and said searches were still underway in the Parisian suburbs where the suspects were rounded up.

"There was an operation led by the DST (the French national counter-espionage service) resulting from a judicial mandate issued by judges Jean-Louis Bruguiere and Jean-Francois Ricard in relation to the Casablanca bombings of May 16, 2003, " said the source.

The two anti-terrorist judges are investigating the Moroccan bombings that killed 45 people, including three French citizens.

The police said Monday's arrests were not linked to the Madrid attacks.

The Paris prosecutor's office released a statement that said the operation was in coordination with Spanish and Moroccan judicial authorities.

Although the suspects had been under investigation for several months, the round up came on a day when security was extremely tight in Paris because of the arrival of Queen Elizabeth II of Britain for a three-day state visit.

Khadija Mohsen-Finan, a researcher at IFRI (French Institute of International Relations) says she is not surprised that the Moroccan Islamic Combatant Group has ties to Islamic groups in France and Spain.

"They communicate by cell phone across international borders," said Mohsen-Finan. "Perhaps they don't even know the person who they receive orders from. But what they share in common is a will to destroy the western culture that has excluded them."

Mohsen-Finan, a sociologist, says Islamic radicals based in Europe are often immigrants from poor neighborhoods and feel frustrated because they cannot take part in the globalization of the culture around them.

She says that even if these groups have proven ties to each other, al Qaeda remains an elusive concept.

"I don't know what al Qaeda is," she said. "Maybe there is no pyramid or chain of command. They can do what they do because of their ability to communicate to each other no matter where they are and because of the hatred they share. These people have a goal of wanting to destroy and they do it in the name of Islam. Years ago, the same type of people were called Nihilists."

The Moroccan Islamic Combatant Group is listed by the U.S. as a terrorist organization with links to al Qaeda.

On Saturday in Madrid, five terror suspects, including the two supposed ringleaders of the train bombings, blew themselves up when police approached their house.

Also during the weekend, a Spanish newspaper received a faxed letter threatening to "declare war" on Spain and turn the country "into an inferno" if it did not withdraw its troops from Iraq and Afghanistan and ceased to support the United States.

The letter, received by the daily ABC , gave Spain until April 4 to withdraw its troops.

Spain announced on Monday the arrest of two more suspects linked to the March bombings.

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