BEIRUT—As hundreds of thousands of people gathered for the funeral of slain Hezbollah leader Hassan Nasrallah in Beirut on Sunday, its current chief vowed to continue fighting Israel as the group projected its power despite an Israeli offensive that has left it weakened and in disarray.

The long-delayed funeral for Hezbollah’s leader Hassan Nasrallah is taking place Sunday, nearly five months after he was killed in a massive Israeli airstrike on the southern suburbs of Beirut.

Hundreds of thousands of people packed into a stadium in Beirut and the streets outside Sunday for the funeral of Hezbollah's former leader, Hassan Nasrallah, nearly five months after he was killed in an Israeli airstrike.