ZURICH (Reuters) - Swiss police raided several houses and searched a mosque in the southern canton of Ticino on Wednesday as part of an investigation into suspected Islamist activity, federal prosecutors said.

More than 100 officers took part in the operation and arrested one man, the Office of the Attorney General (OAG) said in a statement.

The OAG said it was conducting criminal proceedings against two men, one with dual Swiss-Turkish citizenship and the other a Turkish citizen, based on suspicions of recruiting for Islamic State or associated groups.

One of the men was detained pending further enquiries, although the OAG did not specify which one.

The operation was part of an independent Swiss investigation and was unconnected to the truck attack at a Berlin Christmas market that killed 12 people in December, the OAG said.

Amis Amri, the Tunisian asylum seeker who drove the truck, had several links to Switzerland, and may have obtained a gun in the country.

The OAG has opened its own investigation against “unknown” persons in relation to the Germany attack.

Neutral Switzerland is not a primary target for Islamist attacks because it is not part of the military campaign against groups such as Islamic State, but the security threat level has been elevated, the NDB federal intelligence service said in its annual report last year.

The Swiss took a suspected Islamist leader into custody last year in their first arrest of a senior figure from a Salafist ring based in the northern city of Winterthur.

Authorities said Wednesday’s operation was not linked to Winterthur.

Swiss authorities believe more than 70 people have traveled to the Middle East to become jihadist fighters since 2001.

A Swiss court last year sentenced three Iraqis for terrorism offences, a verdict that the senior prosecutor said should send a message to jihadists not to see the country as an easy target.

The three main defendants, who had denied wrongdoing, were arrested in early 2014 on suspicion of planning terrorist attacks and helping Islamic State militants enter the country.