(CNN) A gunman walked into an Islamic center in central Zurich and shot three men, police in the Swiss city said Monday.

The man, decked out in dark clothing, opened fire on a group of worshipers standing inside a prayer room at about 5:30 p.m., police said, citing eyewitnesses. The shots injured the men, some seriously, Zurich police said in a news release.

The gunman fled and police blocked off the area, not far from the central train station. Witnesses said the shooter, who is still being sought, appeared to be about 30 years of age and was wearing a dark wool cap. The victims are aged 30, 35 and 56.

Police didn't disclose any potential motive.