GINOWAN, Okinawa — Almost 24,000 people surrounded Marine Corps Air Station Futenma here Sunday, forming a 6.8-mile human chain to demand the air base close.

The event was part of a weekend of peaceful anti-base actions to mark the 33rd anniversary of Okinawa’s return to Japan after 27 years of post-World War II U.S. occupation. Also staged Sunday: three protest marches across the island with brief rallies in front several U.S. military bases and a mass afternoon rally at the Ginowan Convention Center.

MCAS Futenma sits in the middle of urban Ginowan. Japan and the United States agreed in 1996 to close the base within seven years once a place for Marine air operations was found elsewhere. A site was found in rural northeast Okinawa but construction has run into protracted delays. An August Marine helicopter crash on a university campus next to Futenma sparked new calls to close it. Last week, a congressional commission studying U.S. military bases overseas recommended the project be abandoned and the Marines move to nearby Kadena Air Base or MCAS Iwakuni near Hiroshima.

Marine officials say they support closing Futenma if an alternate site meets with their operational needs.

The air station gates were closed during Sunday’s event. Demonstrators, some representing political parties, unions and neighborhood associations, joined hands and encircled the base at 2:15 p.m., 2:30 p.m. and 2:45 p.m.

Keiko Itokazu, an Okinawan member of Japan’s House of Councilors, said, “It is abnormal to keep such a dangerous and aging military base in the center of this overpopulated city. ... Futenma air station should be closed as the first step of a visible reduction of the burden shouldered by Okinawa.” She said that 60 years after the Battle of Okinawa, World War II’s last major Pacific engagement, the U.S. military still occupies a fifth of the island.

Nearby, Hatsu Zukeran, 71, waited to join hands with her husband, son and two grandsons. “I have eight grandchildren,” she said. “For them, I want to make Okinawa a peaceful place.”

Kozen Gibo, 64, of Yomitan, held his grandson Takumi, 5, as they awaited word to form the chain. “The U.S. military bases have been here since I was a small child,” Gibo said. “I brought my grandson with me today so he would see that many people on Okinawa do not want military bases on our island.”

Up the line, Mitsuko Tomon, an Okinawan member of Japan’s House of Representatives, said she recently returned from her second trip this year to Washington, D.C., to lobby for reducing the U.S. presence on Okinawa. “This encircling demonstrates the wishes of the people of Okinawa,” she said. “They are clearly calling out that they want the air station closed and the Japanese government to abandon the project for a new base.”

After the rally, Ginowan Mayor Yoichi Iha called the demonstration — the fourth encircling of the base since 1995 — “a great opportunity to get our message out at a time when both governments are engaging in talks over the realignment of U.S. forces in Japan.”