Swiss police have raided the offices of several companies in cantons Ticino and Graubünden as part of an anti-terrorism investigation.

Officials also confirmed that three private homes were also searched on Thursday in a simultaneous police operation involving around 60 officers.

No arrests were made in the daytime raids, but police say a number of documents have been seized.

Federal authorities gave the green light to Thursday's raids on an unknown number of offices after suspicions were raised that one or more companies may be involved in the direct or indirect financing of terrorist activity.

Hansjürg Mark Wiedmer, a spokesman for the Federal Prosecutor's office, said the operation had proceeded according to plan.

"It was a successful operation, and we got all the documents we wanted," Wiedmer told swissinfo.

"I can't give any details about the documents seized, because we will now analyse them and until we have done so we can't comment on the content of them," he added.

Ongoing investigation

The Federal Prosecutor's Office opened a lengthy investigation into terrorist activity in the autumn of last year in the wake of the September 11 attacks in the United States.

Wiedmer refused to elaborate on whether more raids were likely in the future, but confirmed that the investigation was ongoing.

"The investigation is continuing full force and if we have any indication or suspicion of financing of terrorism, we will proceed and bring people to justice - that's our job," Wiedmer said.

Swiss authorities have previously blocked 69 bank accounts containing some SFr34 million ($20.4 million) belonging to organisations or individuals on a list of those suspected of terrorist links.

In addition, Switzerland is carrying out a criminal investigation into Nada Management, a Ticino-based firm which is accused by the United States of helping to fund Osama bin Laden's al-Qaeda network.

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