Okinawa has marked the anniversary of its return to Japan after decades of post-World War II U.S. occupation amid snubs from Tokyo and growing concerns over the concentration of the roughly 25,000 U.S. forces still on their islands.

Tensions between Okinawans and the central government in Tokyo are longstanding, but Wednesday's anniversary of the May 15, 1972, reversion comes at a particularly awkward time. Protests were planned in Tokyo and there were no official ceremonies in Okinawa.

Last month, Prime Minister Shinzo Abe made a point of celebrating the end of the U.S. occupation of Japan proper — which came 20 years before Okinawa's — and the mayor of Japan's second-largest city earlier this week suggested U.S. troops on Okinawa should take advantage of sex workers to relieve their frustrations.