Americans visiting Mexico City are strongly advised to use only taxis from authorized stands because of an increase in the frequency and violence of robberies during rides in unauthorized cabs, the State Department said Tuesday.

A department announcement said growing numbers of U.S. Embassy employees and tourists have been assaulted, abducted and robbed after hailing Volkswagen “Bug” taxis and other cabs cruising the streets or parked in front of restaurants, theaters and hotels.