Hamas has named Yahya Sinwar as its new overall chief, replacing Ismail Haniyeh who was killed in Tehran last week.

Since 2017, Sinwar has served as the group’s leader inside the Gaza strip. He will now become leader of its political wing.

It is believed Sinwar remains in the Gaza strip, though his current whereabouts are unknown.

The announcement comes at a moment of heightened tension in the Middle East, as Iran and its allies threaten retaliation for the killing of Haniyeh, which they blame on Israel. Israel has not commented.

“The Islamic Resistance Movement Hamas announces the selection of leader Yahya Sinwar as the head of the political bureau of the movement,” a statement from Hamas said.

Sinwar currently tops Israel’s most-wanted list. Israel’s security agencies believe he masterminded the planning and execution of the 7 October 2023 attacks, which left over 1,200 people dead and 251 taken back into Gaza as hostages.

Details of how Sinwar’s leadership of the group’s political bureau will function are yet to be released by Hamas.

The 61-year-old has not been seen in public since the attacks in October, and is believed to be hiding “10 storeys underground” in Gaza, US Secretary of State Antony Blinken said in June.

In the late 1980s, Sinwar founded the Hamas security service known as Majd, which among other things targeted alleged Palestinian collaborators with Israel.

Sinwar has spent much of his life in Israeli jail – and after his third arrest in 1988 he was sentenced to four life terms in prison.

However, he was among 1,027 Palestinian and Israeli Arab prisoners released by Israel in 2011 in exchange for an Israeli soldier held captive for over five years by Hamas.

He later returned to his position as a prominent leader in Hamas and was appointed head of the group’s political bureau in the Gaza Strip in 2017.

The US includes Sinwar on its blacklist of “international terrorists”.