Israel had by Tuesday expelled most of the 130 pro-Palestinian activists whose entry it has refused in recent days, but 56 remained in a detention facility.
The activists had landed at Ben Gurion International Aiport near Tel Aviv on Friday, as part of a fly-in organized by a coalition of Palestinian civil groups.
Some 25 activists were flown back to Europe on Tuesday, and a Belgian national was allowed in to Israel after he agreed not to visit the West Bank, Immigration Authority spokeswoman Sabine Hadad told the German Press Agency dpa.
Of the 130, four others were allowed in after questioning. The remainder were put on return flights over the past days.
On their return to European airports, many raised allegations about the conditions of their detention. Upon landing in Israel, they say they were crammed into Prison Service vans for up to five hours, without access to a toilet and only receiving water bottles after asking for them.
On arrival at a prison near the southern city of Beersheba, some 16 activists were kept for two more hours in a small cell with just one toilet, before being transferred to a more comfortable open wing.
They complained that for the duration of the transit, they were unable to see lawyers and consuls or make telephone calls.
Israel Prison Service spokeswoman Sivan Weizman said the activists received visits from lawyers and consuls from Saturday morning. She said they were also allowed to see doctors, medics and social workers.
"We don't know of any improper treatment. On the contrary," she told dpa.
Organizers said some 60 to 90 activists made it to the West Bank, some of them because they did not declare openly that they were participants of the Welcome to Palestine Campaign.
Palestinian civil groups had called on foreign supporters to participate in a week of "non-violent resistance," scheduled to end Saturday, against the Israeli occupation. The activists were asked to declare the purpose of their visit openly.
The campaign sought to draw attention to fact that the West Bank can only be reached by plane via Israel, which gives the country the say over who can enter.
Israel declared it would refuse entry to all participants of the Welcome to Palestine campaign, unless they signed documents stating they would not participate in "disturbances of the order."
Organizers said Israel had no right to prevent foreigners from visiting the West Bank and participating in peaceful demonstrations against its occupation of the territory.
Some of the visitors who made it through joined Palestinians in demonstrations over the weekend against Israel's West Bank barrier.
Sergio Yahni, of Welcome to Palestine, said the visitors were touring the divided city of southern Hebron on Tuesday. Dozens of Jewish settlers live under heavy army protection in the heart of the city, one of the locations in the West Bank hardest hit by Israeli security restrictions on Palestinian movement.
The visitors are scheduled to participate in an East Jerusalem march on Friday, in support of declaring Palestinian statehood in September.