GENEVA: The United Nations voiced concern Tuesday that some of the Palestinian detainees released in exchange for Israeli soldier Gilad Shalit may not have been given a choice on where to go and said this could constitute an illegal forced transfer.

The office of Navi Pillay, the U.N. High Commissioner for Human Rights, welcomed Tuesday’s release but cited reports that some of the Palestinian prisoners from the West Bank may be freed only to the Hamas-ruled Gaza Strip or abroad.

Under international humanitarian law, it is illegal to forcibly transfer war detainees or deport them to another country against their will.

Shalit returned home to a national outpouring of joy in Israel Tuesday after five years in captivity, and hundreds of Palestinian prisoners exchanged for him were greeted with kisses from Hamas leaders in the Gaza Strip.

“It was with a sense of great relief that we have received news of the agreement to exchange prisoners. We do however have concerns regarding reports that hundreds of Palestinian prisoners from the West Bank may be released to the Gaza Strip or abroad,” Pillay’s spokesman Rupert Colville told Reuters in response to a query.

“If in some cases this has been without the free and informed consent of the concerned individuals, this may constitute forced transfer or deportation under international law,” he added. “We are not sure to what extent they consented to this.”

Most of the prisoners were returned to Gaza, an Israeli-blockaded Palestinian enclave controlled by Hamas, an Islamist group that is classified as a terrorist group by the EU and the U.S.

It was not immediately clear whether some of those moved to Gaza were loyal to Fatah, a rival Palestinian faction ruling the West Bank and led by President Mahmoud Abbas.

Turkish Foreign Minister Ahmet Davutoglu said 10 Palestinians would come to Turkey as part of the swap. Some 40 Palestinians were being sent to Turkey, Syria and Qatar.

Over the past days, the International Committee of the Red Cross conducted confidential interviews with all 477 Palestinians being released from Israeli detention centers in this first phase of the swap, an ICRC spokesman said.

“ICRC delegates interviewed each detainee in private prior to his or her release to verify that they accepted their release,” ICRC spokesman Marcal Izard told Reuters in Geneva.

But, speaking in what he said were general terms, he added: “Returning people to places other than their habitual places of residence is in contradiction to international humanitarian law.”

“Choosing between staying in detention or being released to a place other than the detainee’s habitual place of residence cannot be considered as a genuine expression of free will,” he added.

Once the detainees were released by Israel, the independent humanitarian agency facilitated their transport on ICRC buses – from Israel’s Kerem Shalom crossing into the Gaza Strip via Egypt, and into Ramallah in the West Bank, he said.