The Israel Defence Forces (IDF) said Sinwar, considered the mastermind of the 7 October attack just over a year ago, had been "eliminated" in southern Gaza on Wednesday.

Warning: This story contains an image readers may find distressing

The Israeli military also released drone footage which it said showed the final moments of the Hamas leader before he was killed.

Follow the latest Middle East updates

In the video Sinwar, 62 and deemed responsible for last year's massacre of 1,200 people at the hands of Hamas militants in southern Israel, appears injured as he sits in a ruined building.

Sitting on a chair, his face covered in a scarf, he is seen trying to throw an object at the drone.

How the battle unfolded

As more details emerge, it appears the killing was the result of a chance encounter rather than a targeted operation.

Israeli officials said the Hamas leader, who was being hunted by intelligence services for the past year, was killed after he emerged from the group's underground tunnel system as he tried to escape to a safer location.

Read more:
What Sinwar's death might mean for the war
Who was Hamas leader Yahya Sinwar?

They said he was found by infantry soldiers searching an area in the Tal El Sultan area of southern Gaza, where they believed senior members of Hamas were located.

The troops saw three suspected militants moving between buildings and opened fire, leading to a gunfight during which Sinwar escaped into a ruined building.

According to accounts in Israeli media, tank shells and a missile were fired at the building.

Israeli military spokesperson Rear Admiral Daniel Hagari said at this stage he was only identified as a fighter.

Troops entered the ruined building and found him with a weapon, a flak jacket and 40,000 shekels ($10,731.63).

"He tried to escape and our forces eliminated him," Rear Admiral Hagari said during a televised briefing.

His death was confirmed following DNA tests and other checks, like dental records.

There was no immediate confirmation from Hamas of Sinwar's death - but sources within the group have said they have seen indications to suggest he was indeed killed.

According to four Israeli defence officials quoted by The New York Times, Sinwar was killed by a unit of trainee squad commanders who unexpectedly came upon him while carrying out a routine operation in the area.

The Pentagon said US forces had no role in the killing.

Spokesperson Air Force Major General Patrick Ryder said: "This was an Israeli operation. There (were) no US forces directly involved".

He said the US had contributed intelligence relating "to hostage recovery and the tracking and locating of Hamas leaders who have been responsible for holding hostages. And so certainly that contributes in general to the picture."

No telephones

In the last months of his life, Sinwar was believed to have stopped using telephones and other communication equipment that might have allowed Israel's intelligence to track him down.

He was believed to be hiding in the vast network of tunnels that Hamas dug beneath Gaza over the past two decades, but many were uncovered by Israeli troops during the war.

The head of Israel's military, Lieutenant General Herzi Halevi, said Israel's hunt for Sinwar had driven him "to act like a fugitive, causing him to change locations multiple times".

Sinwar's death is a huge blow to Hamas.

The group's military commander Mohammed Deif was killed in an Israeli airstrike on 13 July.