Israel greets pro-Palestinian activists with snide letter NEW: 38 activists have been refused entry, an immigration official says 1,500 to 2,000 Palestinian suppporters want to fly in from Europe, the U.S. and Canada Activists plan to go to events in Bethlehem and other West Bank cities, they say Israel is sending some home with a saracastic letter about the region Jerusalem (CNN) -- Israeli authorities stepped up security at Tel Aviv's Ben Gurion airport Sunday as hundreds of pro-Palestinian activists were due to arrive in the country in a "fly-in" campaign to protest Israel's policies in the West Bank. Some activists were barred from entering the country for refusing to promise not to engage in disorderly conduct, but Israel did allow some other activists to enter, Israeli officials said. By Sunday afternoon, 38 activists had been refused entry at the airport, said population and migration authority spokeswoman Sabin Hadad. Activists and authorities gave conflicting accounts of the situation. Israeli police spokesman Mickey Rosenfeld said four protesters were arrested for attempting to disrupt order at the airport. He said there were 500 police officials there. Mazin Qumsiyeh, a spokesman for the "Welcome to Palestine" campaign, said nine Israeli activists were arrested violently at the airport, and that more than 1,000 uniformed and plain clothes security officers were at the airport, in what he called a sign of "unprecedented Israeli hysteria and paranoia." Activists who were sent home were being given a letter sarcastically thanking them for "choosing to make Israel the object of your humanitarian concerns." The letter says protesters could have focused on "the Syrian regime's daily savagery against its own people," or the actions of Iran or Hamas, according to a copy posted on Twitter by Ofir Gendelman, a spokesman for Prime Minister Benjamin Netanyahu. We therefore suggest that you first solve the real problems of the region, and then come back and share with us your experience. Have a nice flight," the letter says. Organizers of the "fly-in" event said some 1,500 to 2,000 activists mainly from Europe, the United States, and Canada would board civilian flights for Israel in order to make their way to various events in Bethlehem and other West Bank cities. Activists say they are trying to draw attention to what they claim are prejudicial Israeli border policies that force many international visitors coming to Palestinian areas to lie about their destinations. "We believe, like prisoners in prisons, we are entitled to receive visitors and Palestinians under Israeli occupation are also entitled to receive visitors," Qumsiyeh said. So we are entitled to get international visitors to come and visit and show solidarity with us to learn about the situation, but Israel chooses to prevent these people from coming. On Sunday, he said a number of activists had reached the West Bank, but did not say how many. The activists who were denied entry on Sunday were from Portugal, Canada, Switzerland, France, Spain and Italy, Hadad said. Last year, organizers staged a similar event and Israel authorities detained and deported dozens of activists who entered the country. On Tuesday, Israel's public security minister, Yitzhak Aharonovitch called activists "provocateurs" and told Israeli news portal Ynet they would "be dealt with in a determined and quick way," adding that "If they arrive in Israel they will be identified, removed from the plane, their entry into Israel will be prevented and they will be moved to a detention facility until they are flown out of Israel." To that end, Israeli officials have been in touch with airlines and provided them with lists of people who are forbidden from entering the country. "Usually airlines don't allow these people to embark, because then they have to cover the expense of the return flight," said Israeli Foreign Ministry spokesman Yigal Palmor. "What we did last year is we had a list of number of people who have been banned from entering the country in the past, and others who will be banned now because they have openly declared that they will come here to disturb public order in one way or another," Palmor said. Palmor said arriving passengers who are denied an entrance visa have the right to appeal but could face three days in detention before their hearing. On Sunday, one activist in the United Kingdom said she was in a group of 30 passengers who were blocked from boarding a flight from Manchester to Tel Aviv. "Israel was able to stop us, British passport-holders, and Israel has the power to extend its apartheid to other countries and borders," activist Norma Turner said. CNN's Guy Azriel contributed to this report.