(Reuters) - More than 40 pro-Palestinian activists reached Tel Aviv´s international airport on Sunday as part of an attempted "fly-in" only to be detained as Israel denied them entry and scrambled to stop other campaigners boarding flights in Europe.

Israel´s decision to distribute "no-fly" lists to European carriers and deploy of hundreds of police at Ben Gurion airport underlined its deep concern over international campaigns against its treatment of the Palestinians.

Police spokesman Micky Rosenfeld said that 41 people had been refused entry at Ben Gurion airport by early afternoon and would be deported. Four Israeli supporters, two holding "Welcome to Palestine" signs, were also arrested as they waited to greet the arrivals.

An Interior Ministry spokeswoman said Israel on Wednesday had given airlines the names of some 1,200 activists whose entry would be barred. Israel made it clear the carriers would have to bear the costs of repatriating any deportees.

Leehee Rothschild, a "Welcome to Palestine" activist, said dozens of campaigners had since been informed by airlines that their tickets to Tel Aviv had been cancelled.

Organizers had said some 1,200 Palestinian supporters throughout Europe had bought plane tickets to Israel, planning to travel on to the occupied West Bank, an hour´s drive from Tel Aviv, as part of a campaign called "Welcome to Palestine".

The aim of the so-called "flytilla", organizers said, was to help open an international school and a museum in Bethlehem.

But Israel, which described the fly-in as a misguided protest against "the Middle East´s sole democracy", denounced the activists as provocateurs and said it would deny entry to anyone who threatened public order.

NO-FLY ZONE

In Brussels´ Zaventem airport, around 100 Belgian and French activists were not allowed to board flights to Israel.

The activists, some of whom said they wanted to build a new school, held up letters that were handed to them at the airport which said they were on a no-fly list because they intended to "disrupt order and confront security forces at friction points".

Cellphone video uploaded by an activist to the internet showed about 20 pro-Palestinian activists at Charles de Gaulle airport in Paris surrounded by police.

Some Israeli political commentators said Israeli authorities had over- reacted, playing into the hands of pro-Palestinian campaigners seeking publicity.

A similar, though smaller event last year led to a few hundred activists being blocked at European airports and more than 100 others were deported after Israel denied them entry.

"Israel´s willingness to detain people who have not committed any crime and have done nothing but say they came to visit Palestine is a hysterical reaction," Rothschild said.

Palestinians hope to establish a state in the West Bank and East Jerusalem, areas Israel captured in the 1967 Middle East War, and the Gaza Strip that is ruled by Islamist group Hamas.

The office of Israeli Prime Minister Benjamin Netanyahu released a letter on Saturday which it hoped to hand the activists upon their arrival.

Echoing the "thank you for choosing our airline" announcements cabin crew often make to passengers after landing, the letter said: "We appreciate your choosing to make Israel the object of your humanitarian concerns."

It called the activists´ campaign misguided and said they could have chosen instead "to protest (against) the Syrian regime´s daily savagery against its own people".

Israel´s left-wing Haaretz newspaper, criticizing the government´s ban, said it should invite "peace activists to visit anywhere and welcome them with flowers".

(Additional reporting by Claire Davenport in Brussels; Editing by Jon Hemming and Andrew Osborn) (© Thomson Reuters 2012. 04/15/12)