Senior Hamas official Saleh Al Arouri was among those killed on Tuesday night in an Israeli drone strike on Beirut's southern suburbs of Dahiyeh.
Arouri was a senior leader in Hamas's politburo and one of the founding commanders of its military wing, the Qassam Brigades.
Hamas confirmed Arouri's killing via the affiliated Al-Aqsa radio.
Lebanon's state news agency reported that the Israeli drone struck a Hamas office in Dahiyeh, leaving at least four people dead..
Lebanon's caretaker prime minister Najib Mikati condemned the explosion as a "new Israeli crime" and said it was an attempt to pull the country into war.