Israel freed the Hamas speaker of the Palestinian parliament Aziz Dweik on Thursday after holding him without charge since January, sources on both sides said.
"Dr Aziz Dweik was released at the Beit Sira roadblock," in the occupied West Bank, the head of his office, Bahaa Yusef, told AFP.
Israel Prison Service spokeswoman Sivan Weizman confirmed: "Mr Dweik has been released from Ofer prison."
Dweik's lawyer, Fadi Qawasmeh, said Israel had accepted his request not to renew his client's administrative detention for a further six months.
The Israeli army arrested Dweik on January 19 at a roadblock between Jerusalem and the West Bank city of Ramallah.
It said his detention without charge was necessary because of his "presumed involvement in the activities of a terrorist organisation."
Dweik was appointed speaker of the Hamas-dominated Palestinian parliament elected in 2006 but the legislature has been effectively sidelined since the Islamists expelled forces loyal to president Mahmud Abbas from the Gaza Strip the following year.
Administrative detention is a procedure dating back to the pre-1948 British Mandate under which military courts can hold suspects without charge for periods of up to six months, which can be renewed indefinitely.