NEW YORK — Thousands of fast-food workers and their supporters beat drums, blew whistles and chanted slogans Thursday on picket lines in dozens of U.S. cities, marking the largest protest yet.

The nationwide day of demonstrations came after similar actions organized by unions and community groups over the past several months. Workers are calling for the right to unionize without interference from employers and for pay of $15 an hour. That’s more than double the federal minimum wage of $7.25 an hour.