Hamas leader Ismail Haniyeh was killed in Iran by a bomb planted months earlier, according to sources.

Hamas political leader Ismail Haniyeh was killed in Tehran on Wednesday using a bomb that had been secretly placed in the guest house where he was staying, CNN reported. The explosive device, hidden about two months prior, was remotely detonated when Haniyeh entered his room. The Iranian government and Hamas have blamed Israel for the assassination, though Israel has not confirmed involvement. U.S. officials were informed by Israeli counterparts only after the event.

The New York Times first detailed the assassination, which has heightened concerns of escalating conflict between Israel, Hamas, and its allies. Previously, Iranian state media and Hamas had claimed Haniyeh was killed by a rocket fired from outside. The new information about the bomb’s placement inside the guest house, protected by Iran’s Islamic Revolutionary Guard Corps (IRGC), suggests a serious security lapse.

Haniyeh had arrived in Tehran to attend various events, including the inauguration of Iran’s new president. He was last seen publicly at an exhibit at Tehran’s Milad Tower before being killed at 2 a.m. by what was initially reported as an “airborne guided projectile.” His body was flown to Doha for burial on Friday.

The assassination occurred shortly after Israel’s strike on Beirut, which killed Hezbollah commander Fu’ad Shukr. Hezbollah’s leader Hassan Nasrallah warned of an “inevitable” response to Shukr’s death and indicated possible coordination with regional groups. This incident marks a potentially volatile new phase in the ongoing regional conflict involving Israel, Iran, and its allied forces.