Athens , Greece ( CNN ) -- Greek police have arrested the captain of a U.S. ship whose passengers and crew had hoped to help lead a Gaza-bound flotilla aimed at challenging Israel 's maritime blockade of the Palestinian territory . John Klusmire , an American citizen and captain of The Audacity of Hope , was asked to report to a police station Saturday morning , said Jane Hirschmann , an American who is one of the flotilla organizers . A spokesperson with the Greek Coast Guard , who was not named per custom , confirmed Klusmire 's arrest . The reason given was that he had left the mainland without permission and put passengers in danger . He will appear before Greek prosecutors on Tuesday . Hirschmann added that , in addition to disobeying a police order , Klusmire is being charged with disturbing sea traffic . `` This is intimidation , '' she said . `` They 're making an example of our captain to stop other boats in the flotilla from trying to sail . '' His vessel -- which carried 36 American passengers , four crew members and several journalists , including CNN reporter Phil Black -- was intercepted Friday by a Greek Coast Guard patrol vessel roughly 10 minutes after it had departed Perama . The Greek authorities were in a standoff with the crew for about three hours , during which activists sang , chanted and waved signs in support of their mission . The ordeal took a turn , however , when an inflatable boat carrying an armed Greek military commando team told the activists to follow them back to port or face being boarded . Eventually , the ship returned to Greece , where it is now tied up at a Greek naval facility . Four other crew members have been ordered by Greek authorities to stay aboard the ship , Hirschmann said . Many other activist passengers have remained on the vessel as well , in a show of solidarity . The Audacity of Hope is one of 10 ships that organizers hope to unite to form a flotilla heading toward the Middle East . The trip is partially meant to commemorate a May 2010 incident in which Israeli troops boarded Mavi Marmara , a Turkish ship filled with humanitarian aid and 700 activists from various countries . Nine people died in subsequent clashes with Israeli Navy commandos . The Greek government said Friday that it wo n't allow any of the nine other boats in the flotilla to sail to Gaza because their mission is too dangerous . Flotilla members accuse the Greek government of buckling to pressure from Israel 's government . For their part , the Israelis have said they are mounting a diplomatic offensive to try to stop the flotilla from setting sail at all . On Tuesday , the Israeli government said flotilla participants had threatened to kill Israeli military personnel should their boats be boarded . They alleged that the participants were stockpiling sacks of sulfuric acid on boats to be used in the event of any attacks on Israeli commandos . Flotilla organizer Medea Benjamin dismissed the allegations as ludicrous , saying : `` They see this nonviolent , rag-tag group of ships as such a threat they 're using their entire propaganda apparatus , and their diplomatic and economic clout to try to stop 300 peace activists . It 's pathetic . '' The Middle East Quartet -- composed of officials from the United States , United Nations , European Union and Russia -- on Saturday issued a joint statement asking `` all governments concerned to use their influence to discourage additional flotillas , which risk the safety of their participants and carry the potential for escalation . '' The Quartet added in its statement that it `` strongly urges all those wishing to deliver goods to the people of Gaza to do so through established channels , so that their cargo can be inspected and transferred via established land crossings . '' Doing so , the group contends , is the best way to both help Palestinians and address Israel 's `` legitimate security concerns . '' Journalist Elinda Labropoulou contributed to this report .
NEW : The Quartet urges all governments to discourage additional flotillas . The captain of The Audacity of Hope has been arrested , Greek authorities say . Comment: His ship is one of 10 in a flotilla meant to challenge Israeli 's blockade of Gaza .