Israeli authorities said Thursday they denied a request by a top Hamas leader to allow his three sisters living in Israel to travel to the Gaza Strip to attend his son's wedding, hinting the decision was because some Israelis are still missing in Gaza.

The Israeli defense body COGAT said that Ismail Haniyeh's request was denied because of "Israeli humanitarian cases" in Gaza -- apparently a reference to two Israeli citizens who Israel says are being held in Gaza, as well as the remains of Israeli soldiers Hamas is said to have from last summer's war.

The Hamas leader's sisters live in Israel because they married members of Israel's Arab minority before the first Palestinian Intifada erupted in 1987, when travel between Israel and Palestinian areas was easier. Haniyeh's son Amir is to be married later Thursday.

Hamas and Israel are bitter enemies and have fought three wars since Hamas violently wrested control of Gaza in 2007 from forces loyal to the Western-backed Palestinian President Mahmoud Abbas. Since then, Hamas has ruled Gaza while Abbas governs parts of the West Bank.

Israel, along with Egypt, later imposed a blockade on Gaza. Israel says the blockade is vital to prevent Hamas getting weapons, while critics say it is collective punishment.

Israel limits travel between Gaza and Israel citing security concerns but makes exceptions for humanitarian cases. Haniyeh's sisters have traveled to Gaza in the past.

Hamas officials were unavailable for comment on Thursday.