ZURICH - Swiss police on Tuesday arrested two men in an investigation of possible links to the main suspect in a shooting attack in Vienna that killed at least four people, authorities said.The 18-year-old and 24-year-old men, arrested in the city of Winterthur about 10 kilometers (6 miles) from Zurich, are Swiss citizens, police said in a statement. Swiss Justice Minister Karin Keller-Sutter, in a panel discussion hosted by the Swiss newspaper St. Galler Tagblatt and shown on its website, said the men were "obviously friends" with Kujtim Fejzulai, the 20-year-old Austrian-North Macedonian dual national suspected of the Vienna attack. Keller-Sutter added the men had met in person, without saying when."The two men were arrested on Tuesday afternoon in coordination with the Austrian authorities," Zurich cantonal police said. "The extent to which there was a connection between the two arrested persons and the alleged assassin is currently the subject of ongoing clarifications and investigations which are being carried out by the responsible authorities."Keller-Sutter's office did not immediately return an email seeking further comment.Zurich cantonal police, members of the Federal Police and the city police in Winterthur were involved in the law enforcement operation, the statement said.So far, at least 14 people have been arrested in Austria following raids on 18 properties after the deadly rampage in the center of Vienna on Monday night.Winterthur has been the focus of several law enforcement actions in Switzerland centering on suspected extremists.In September, a man dubbed the "Emir of Winterthur" by Swiss media, and described by prosecutors as a leading figure among Islamist militants in Switzerland, was sentenced to 50 months in prison or supporting and recruiting for Islamic State.