Iran’s security chief Ali Larijani was killed by Israel, the government confirmed on Tuesday, the most senior figure targeted since the U.S.-Israeli war’s first day, while a senior Iranian ​official said Iran’s new supreme leader rejected de-escalation offers conveyed by intermediary countries.

Larijani was widely viewed as one of Iran’s most powerful figures and a confidant of slain Supreme Leader Ayatollah Ali Khamenei and his ‌son and successor, Mojtaba. The security chief had a reputation for pragmatic relations with other factions in the ruling system and foreign diplomats.

Ayatollah Ali Khamenei’s son Mojtaba was chosen by Iran’s Assembly of Experts to succeed his late father as supreme leader, more than a week ‌after he was killed in an air strike, Iranian media reported.