GENEVA, May 6 (Xinhua) -- The United Nations on Wednesday demanded Israel "immediately and unconditionally" release two activists taken from a Gaza-bound flotilla.

Thameen Al-Kheetan, spokesperson for the UN Human Rights Office, said in a statement that the two individuals, Saif Abukeshek and Thiago de Avila, were detained in international waters and transferred to Israel, where they remain held "without charge."

"It is not a crime to show solidarity and attempt to bring humanitarian aid to the Palestinian population in Gaza, who are in dire need of it," he said.

He also voiced concern over what he described as "disturbing accounts" of severe mistreatment of the two detainees, calling for investigations and for those responsible to be held accountable.

The spokesperson also urged Israel to end its use of "arbitrary detention and of broadly and vaguely defined terrorism legislation" that is inconsistent with international human rights law.

In addition, he called on Israel to lift its blockade on Gaza and to allow the entry of sufficient humanitarian assistance into the Strip. ■