Four pro-Palestinian activists were denied entry into Israel after arriving on a flight from Switzerland on Sunday, as part of the "flytilla" protest.
One of those denied entry "is a leader of the activists" police said.
Hundreds of unarmed police officers were guarding the airport, with anywhere from 500 to 1,000 activists in total expected to try to land in Israel, according to police estimates.
Israel plans to bar entry to some 2,000 activists total from at least 15 different countries, mostly in Europe, either by preventing them from boarding their flights or by deporting them once they arrive.
The activists want to draw attention to Israel’s practice of barring foreigners it believes could cause trouble by engaging in pro-Palestinian activities during their visit.
Jpost.com staff contributed to this report
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