Concerns grew among Israelis on Wednesday over the fate of dozens of hostages still held captive in Gaza following the killing of Hamas chief Ismail Haniyeh in Tehran.

Haniyeh's killing "was a mistake as it threatens the possibility of having a hostage deal," said Anat Noy, a resident of the coastal city of Haifa, in her 50s.

"We woke up today with a sense of fear in our hearts that this can escalate even more. There is no calm... we are afraid."

Pakistan said Wednesday the killing of Hamas's political leader in an air strike in neighbouring Iran blamed on Israel was a "reckless act", while hundreds of supporters of an Islamist party held a symbolic funeral near Islamabad.

Describing the assassination of Ismail Haniyeh as "terrorism", Islamabad's foreign ministry said in a statement that "Pakistan views with serious concern the growing Israeli adventurism in the region."

"Its latest acts constitute a dangerous escalation in an already volatile region and undermine efforts for peace", it said.

The killing of Hamas leader Ismail Haniyeh in an air strike in Tehran Wednesday came as a "thunderbolt" to war-weary Gazans, with some expressing disappointment Iran was unable to "protect him".

"This news is like a thunderbolt, something unbelievable," said Wael Qudayh, 35, a resident of the central city of Deir al-Balah.

On Wednesday, Hamas and the Iranian Revolutionary Guards announced that Haniyeh had been killed in Tehran in an Israeli air strike.

He was in the Iranian capital to attend the swearing-in on Tuesday of President Masoud Pezeshkian.

The killing of Hamas political leader Ismail Haniyeh in an air strike in Tehran on Wednesday blamed on Israel has stunned the international community.

Israel has not commented on the death but many countries have warned that it could help turn the Gaza war into a regional conflict.

Here are some key reactions:

- Iran leader vows 'harsh punishment' -

Haniyeh had been in Tehran to attend the inauguration of President Masoud Pezeshkian and Iran's supreme leader Ayatollah Ali Khamenei vowed "harsh punishment" for Israel.

Hezbollah said Wednesday that senior military commander Fuad Shukr was inside a south Beirut building hit by Israel the previous day but that his fate remained unknown.

The strike, which was followed by another, hours later, which killed Hamas political leader Ismail Haniyeh in Tehran, triggered fears the war in Gaza could escalate into a region-wide conflict.

Ismail Haniyeh, who was killed in an Israeli strike in Iran, was the head of Hamas's political wing and a former Palestinian prime minister whose membership of the Islamist militant group dated back to its inception.

Hamas announced his death on Wednesday, saying in a statement: "Brother, leader, mujahid Ismail Haniyeh, the head of the movement, died in a Zionist strike on his residence in Tehran after he participated in the inauguration of the new (Iranian) president."

Hamas said Wednesday its political leader Ismail Haniyeh was killed in an Israeli strike in Iran, where he was attending the swearing-in of the new president, and vowed the act "will not go unanswered".

Iran's supreme leader Ayatollah Ali Khamenei too threatened "harsh punishment" for Haniyeh's killing, saying: "We consider it our duty to seek revenge for his blood as he was martyred in the territory of the Islamic Republic of Iran."

Anger simmered Tuesday after Israel struck a southern Beirut suburb that is also a Hezbollah stronghold, with young men chanting in support of the group at the site of the strike.

Israel hit Hezbollah's stronghold in retaliation for rocket fire from Lebanon that killed 12 children over the weekend in the occupied Golan Heights, saying it had targeted the commander responsible for the attack.

US Vice President Kamala Harris, the presumptive Democratic election nominee, said Tuesday that Israel had a "right to defend itself" following a strike in Hezbollah's stronghold in southern Beirut.

Harris -- who last week struck a tough tone with Israeli Prime Minister Benjamin Netanyahu over Israel's war on Gaza -- also called for a diplomatic solution to reduce the risk of all-out conflict on the Lebanon-Israel border.

Israel's military police on Tuesday questioned soldiers who were arrested on suspicion of sexually abusing a Palestinian detainee, a day after far-right protesters stormed two army bases in support of the troops.

Outside the military tribunal in Beit Lid, dozens gathered for a second consecutive day to protest the arrest of the nine soldiers, in a case that has gripped Israeli media.