The Israeli public broadcaster KAN alleged that the bodies of Sinwar and ten of his aides were found in an underground tunnel in Khan Younis.
Israeli media earlier reported that Sinwar and several Hamas commanders were killed in Israeli air attacks near the European Hospital in Khan Younis several days ago.
There was no immediate Hamas comment on the Israeli claim.
Yahya Sinwar, the head of Hamas in Gaza, was killed by Israeli army in southern Gaza on Oct. 16, 2024.
The Israeli army has pursued a brutal offensive against Gaza since Oct. 7, 2023, killing more than 53,300 Palestinians, most of them women and children.
The International Criminal Court issued arrest warrants last November for Israeli Prime Minister Benjamin Netanyahu and his former Defense Minister Yoav Gallant for war crimes and crimes against humanity in Gaza.
Israel also faces a genocide case at the International Court of Justice for its war on the enclave.
