Israel has blocked an attempt by international activists to organize a high-profile, humanitarian visit to Palestinians in the West Bank.
More than 200 pro-Palestinian activists in Europe were barred from boarding flights to Tel Aviv, after Israel sent a blacklist. Israeli authorities warned foreign airlines that activists were planning anti-Israel protests and disruptions at the airport and they would not be allowed into the country.
Some activists who managed to arrive in Israel were detained and face deportation.
Police said the 20 activists who made it to Ben Gurion Airport, near Tel Aviv, arrived from Switzerland, to be detained by security forces who were expected to expel them.
Organizers of the fly-in deny they were attempting to cause trouble. They say it is a peaceful mission to show solidarity with Palestinians in the West Bank, which can only be reached by traveling through Israel.
American Laura Durkay of New York, who was in England trying to board a flight to Israel, said Israel is treating peace activists like terrorists.
"You know we are not doing anything illegal. We are not doing anything dangerous. We do not pose any threat to anyone," she said.
Israel deployed 600 police officers at the international airport to prevent unrest.
Public Security Minister Yitzhak Aharonovich said authorities would take all the necessary measures to prevent "hooligans" from entering the country and disturbing the peace.
The fly-in follows an attempt by hundreds of pro-Palestinian activists to organize an aid flotilla to challenge Israel's blockade on the Gaza Strip. The flotilla fizzled after Greece banned the ships from sailing from its ports.
Israel described the fly-in and the flotilla as provocations aimed at de-legitimizing the Jewish state. Activists say both events point to international complicity in enforcing the Israeli occupation of the Palestinian territories.