Ismail Haniyeh led Hamas, the Palestinian group that runs Gaza, for over a decade. Hamas said he was killed in Tehran after attending the inauguration of Iran’s president.

Hamas said its political leader has been killed in an overnight strike in the Iranian capital Tehran, a major development that throws the war between Israel and the militant group into an unpredictable and dangerous new phase.

Iran’s supreme leader and representatives of Palestinian militias he backs prayed Thursday over the coffins of Hamas leader Ismail Haniyeh and his bodyguard who were killed in a shocking assassination blamed on Israel that risked escalating into an all-out regional war.