More reaction now from Iran - the country's Foreign Ministry Spokesperson Nasser Kanani has expressed condolences over the death of Haniyeh, describing him as a "proud fighter".

According to the Iranian Foreign Ministry website, Kanani says Haniyeh's blood "will never be wasted".

He says Iran is investigating - but the death will "strengthen the deep and unbreakable bond" between Iran and the Palestinians.

Rushdi Abualouf, the BBC's Gaza correspondent who is currently in London, says Haniyeh was seen by many as a "more pragmatic leader" of Hamas.

He says Haniyeh had visited Tehran between 10 and 15 times since becoming the group's overall leader about six years ago, and "he must have felt safe going there".

Our correspondent says he spoke to Hamas officials this morning, and they were "in a state of shock", giving different accounts of what exactly happened.

Ismail Haniyeh had arrived in Tehran on Tuesday to attend the inauguration of Iranian President Masoud Pezeshkian, who won the elections earlier this month.

Here are some scenes from his visit - just hours before his death in the early hours of this morning.

Image source, EPA

Image source, EPA

Image source, Reuters

Hugo Bachega
Middle East correspondent, in Beirut

The killing of Ismail Haniyeh in Tehran, where he was attending the inauguration of the new Iranian president, is another significant – and dangerous – development that will renew fears of an escalation of violence across the Middle East.

Hamas says he was targeted by Israel, which has not commented.

It came just hours after Israel carried out an attack in Beirut, hitting the base of the powerful Iranian-backed Lebanese militia and political movement Hezbollah.

The Israeli military claims it killed senior commander Fuad Shukr, describing him as the right-hand man to the Hezbollah leader, although Hezbollah has not yet confirmed it.

It is not clear how Hezbollah - which has an estimated 150,000 missiles and rockets - will react. Having a high-profile figure targeted in its stronghold may be seen as a provocation too far, and a reaction is almost inevitable.

Until now, most of the violence between Israel and Hezbollah has been contained to areas along the Lebanon-Israel border. But there have been fears that the fighting could escalate into a major conflict, and involve other Iranian-supported groups in the region.

So far, both Israel and Hezbollah have indicated that they are reluctant to be drawn into an all-out war, which could have catastrophic consequences for Lebanon, Israel and the region as a whole.

Image source, Reuters

Away from Haniyeh's death for a moment, we've also got more to bring you on the Israeli strike in Lebanon yesterday - which Israel claims killed senior Hezbollah commander Fuad Shukr.

Hezbollah's just released a statement on that strike saying "a number of citizens" were killed, others were injured and "great destruction" caused.

They confirm Shukr was in the building, saying: "The great jihadist leader, brother Sayyid Fuad Shukr (Haj Mohsen) was then in this building."

But Hezbollah says they "have been working to lift the rubble steadily, but slowly" - and they are still waiting to discover "the fate of the great commander".

The assassination of senior Hamas figure Ismail Haniyeh was carried out by a guided missile targeting his private residence in Tehran, sources from Saudi outlet Al Hadath say.

The news outlet reports the missile hit the building at around 2:00 local time (23:30 BST) - something that Iran state media also says.

Fars news, which is affiliated with Iran's revolutionary guard, also says Haniyeh was stationed in a residence for veterans in the north of Tehran, and that he was killed by "a projectile from the air".

Image source, Reuters

US Defense Secretary Lloyd Austin has just reiterated that he doesn’t think a wider conflict in the Middle East is inevitable.

"I don't think war is inevitable. I maintain that. I think there's always room and opportunities for diplomacy," Austin tells media during the last day of a trip to the Philippines.

Austin does not comment on reports of Haniyeh's death, saying only that he didn’t have "any additional information to provide" on the matter.

And when asked about how Washington might support Israel in the event of an expanding regional conflict, Austin says that the goal was still to de-escalate tensions and "take the temperature down".

We haven't had a direct response from Israel yet to Haniyeh's death.

But Daniel Hagari, a spokesman for the Israel Defense Forces (IDF), says that "there are no changes in the home defence policy".

In a post on X, he wrote: "At this time, the IDF is conducting a situation assessment. If any changes are decided, we will update the public immediately."

We're now hearing some reaction from other countries to this morning's news.

Russia's foreign ministry describes Haniyeh's killing as "completely unacceptable political murder", according to state broadcaster Ria.

The country's deputy foreign minister, Mikhail Bogdanov, says the Hamas leader's death "will lead to further escalation of tensions".

Meanwhile, Turkey's foreign ministry also condemns the "shameful assassination in Tehran", saying in a statement quoted by Reuters that "this attack also aims to spread the Gaza war to a regional dimension".

The killing of key Hamas leader Ismail Haniyeh has brought the region closer to an all-out war than any time before, Nader Hashemi, a professor of Middle Eastern Studies at Georgetown University, tells the BBC.

"This is a major development," he says. "I think it also impacts events in Lebanon because just a few hours earlier Israel tried to assassinate a senior Hezbollah leader in southern Beirut and the working assumption was that Iran and Hezbollah were not interested in escalation."

But Haniyeh's assassination has upended those calculations, he adds. "Now Iran has every incentive to try and escalate this conflict."

Israel yesterday claimed to have killed Fuad Shukr, a senior leader of the armed group Hezbollah.

Palestinian President Mahmoud Abbas has called the assassination of Haniyeh "a cowardly act and a dangerous development".

He also called on Palestinians "to unite, be patient and steadfast in the face of the Israeli occupation" in a statement carried by state news agency Wafa.

Abbas's Palestinian Authority governs the West Bank with limited self-rule, and Israel has overall control.

Image source, Reuters

In the last hour, Hamas groups on social media site Telegram have put out an undated clip of Ismail Haniyeh speaking in what appears to be an interview with television network Al Jazeera.

It was accompanied by a quote attributed to Haniyeh where he says "we feel the weight of the responsibility" of the Palestinian issue and are "prepared for these costs... martyrdom for the sake of Palestine".

Haniyeh’s death comes just a hours after Israel claimed it killed the top military commander of Hezbollah, a Lebanon-based group, also backed by Iran.

Israel said it killed Fuad Shukur in an airstrike, in retaliation for a rocket attack in the Israeli-occupied Golan Heights at the weekend.

Hezbollah denied any involvement in that attack - which killed at least 12 people, mostly children - and is yet to confirm Shukur died in the strike on Beirut.

The latest tensions on Israel's northern border have sharply escalated fears of a new war in the region. We explain what's happening here.

Click the play button at the top of the page to watch the BBC's live coverage of Ismail Haniyeh's death.

It's unclear yet what effect this will have on warpublished at 05:58 British Summer Time 31 July

05:58 BST 31 July

Yolande Knell
Middle East correspondent, in Jerusalem

Since the deadly 7 October attacks, Israel has targeted the leaders of Hamas, but so far, apart from killing one senior figure based in Beirut, it’s been unable to reach those at the top of its most wanted list.

But this morning Hamas said its political leader had been killed in “a treacherous Zionist raid".

Last night, Ismail Haniyeh - who was from Gaza but has lived outside for several years - was with the heads of other regional armed groups, backed by Iran, at a ceremony for the swearing-in of the country’s new president.

Few details have been given about the attack which killed him and a bodyguard, but it would have been carefully planned.

Israeli’s military says it doesn’t comment on reports in foreign media. But one Hamas official has called this assassination a “grave escalation.” Another described it as a “a cowardly act that would not go unpunished.”

It’s unclear, as yet, what effect this will have on the course of the war in Gaza, but Haniyeh had been overseeing talks on a new ceasefire and hostage release deal.

Despite his tough rhetoric, he was generally seen by analysts as moderate and pragmatic, compared to the more hardline Gaza-based leaders Mohammed Deif and Yahya Sinwar, who are believed to have masterminded last year’s shocking assault on southern Israel.

If you're just joining us, here's what we know so far about the death of Hamas's leader Ismail Haniyeh:

• In a statement on Wednesday morning, Hamas said Haniyeh had been killed by an Israeli raid while on a visit to Tehran to attend the inauguration of President Masoud Pezeshkian
• Iran's Revolutionary Guard Corps has also confirmed his death
• Israel's military and senior figures within its government are yet to respond to the allegation
• The death of Haniyeh - who had long led Hamas's political operations while living in exile in Qatar - has dealt a severe blow to the Palestinian group
• It comes just hours after an Israeli strike on a senior Hezbollah commander in Beirut, in retaliation for a rocket attack in the Israeli-occupied Golan Heights over the weekend that killed 12 people
• The targeted attacks on two senior Iran-backed militant leaders in the space of 24 hours has raised fears of further conflict in the region
• A senior Hamas official has said that the group will respond to Haniyeh's assassination, calling it "a cowardly act that will not go unpunished"
• Israel has repeatedly vowed to "destroy' senior figures within Hamas's leadership, following the 7 October raid near the Israel-Gaza border, which left 1,200 people dead and saw hundreds taken hostage

The IDF or Israel Defence Forces has told several media outlets - including CNN and newswire Agence France-Presse - that it won't respond to foreign media reports on Haniyeh's death.

Israel has not issued an official statement on Haniyeh's death but there has been reaction from some politicians such as heritage minister Amichay Eliyahu, a member of Israel's far right.

He wrote on X that Haniyeh's death "makes the world a better place".

Eliyahu starts his post on X, external saying: "This is the right way to clean the world from this filth," before going on to say "no more imaginary peace/surrender agreements, no more mercy for these mortals".

He also says "the iron hand that will strike them" will "strengthen our ability to live in peace with those who desire peace".

Israel and Iran have long been engaged in a shadow war - often attacking each other without admitting responsibility.

But Iran believes Israel has also carried out several targeted assassinations on its soil.

Some of the most notable cases include the killing of Iran’s top nuclear scientist Mohsen Fakhrizadeh by a remote-controlled weapon in 2021, and the shooting of a Commander of Iran’s Revolutionary Guards, Col. Sayad Khodai, in Tehran in May 2022.

A senior Hamas official has vowed that the group will respond to Haniyeh's assassination.

Moussa Abu Marzouk called the raid a "cowardly act that will not go unpunished," according to the Hamas-run Al-Aqsa television channel.