Hamas has named Yahya Sinwar as the new head of its political bureau, elevating the hardline militant to the group’s top post after the assassination in Teheran of its previous political leader.

Sinwar’s appointment was announced in a brief statement by Hamas on Tuesday that was aired on pro-Hamas Iranian state media channels.

Sinwar, the Hamas military leader who is seen as the mastermind behind the 7 October attack against Israel, is believed to be hiding in the series of tunnels underneath Gaza. He is the group’s chief decision-maker in Gaza, and is believed to hold control over the estimated 120 Israeli hostages who are still in Hamas’s custody.