A high-level security official in Lebanon told AFP that Saleh al-Aruri was killed along with his bodyguards in a strike by Israel, which has vowed to destroy Hamas after the movement's shock October 7 attacks.
A second security official confirmed the information, while Hamas TV also reported Israel had killed Aruri in Lebanon.
Israeli army spokesman Daniel Hagari did not directly comment on the killing, but said afterwards that the military was in "very high state of readiness in all arenas, in defence and offence. We are highly prepared for any scenario."
Israel has previously announced the deaths in Gaza of Hamas commanders and officials during the war, but Aruri is the most high-profile figure to be killed, and his death came in the first strike on the Lebanese capital since hostilities began.
The strike adds to widespread fears that the nearly three-month-old Israel-Hamas war could become a wider regional conflagration.
Hamas said Aruri's death would not lead to its defeat, while its Lebanon-based ally Hezbollah vowed the killing would not go unpunished, calling it "a serious assault on Lebanon... and a dangerous development".
Lebanese Prime Minister Najib Mikati condemned the killing and said it "aims to draw Lebanon" further into the war.
Aruri, who lived in exile, is accused by Israel of masterminding numerous attacks.
Following his death, Hamas chief Ismail Haniyeh said that a movement "whose leaders fall as martyrs for the dignity of our people and our nation will never be defeated".
Hamas's bloody October 7 attack on Israel resulted in the deaths of around 1,140 people, most of them civilians, according to an AFP tally based on official Israeli figures.
Militants also took around 250 hostages back to Hamas-ruled Gaza, of whom 129 remain in captivity, according to Israeli figures.
After the attack, the worst in its history, Israel began a relentless bombardment and ground offensive that has killed at least 22,185 people, mostly women and children, according to Gaza's health ministry.
Red Crescent struck
Israel's army said soldiers in Gaza had killed "dozens of terrorists" in fighting on Tuesday, and had also raided a weapons storage compound in the southern city of Khan Yunis.
In the aftermath of a strike on the Nuseirat refugee camp in central Gaza, Palestinians rushed to rescue victims and retrieve bodies from the rubble.
"There are about 12 martyrs until now, mostly children. What was their fault? Among them my one-month-old son, what did he do to Israel?" asked Ghazi Darwish. "My other son is five years old, he was also martyred."
Further south in Khan Yunis, the Palestine Red Crescent Society said Israel had twice struck its headquarters, resulting in "five casualties and three injuries" among displaced people who had sought refuge there and at a nearby hospital.
"They told us to go to the south, which is safe, but they are liars," shouted Fathi al-Af, pointing to his wounded daughter on a stretcher on the floor of Nasser Hospital after the Red Crescent strike.
The head of the World Health Organization (WHO) denounced the alleged strikes as "unconscionable".
United Nations agencies have voiced alarm over Gaza's spiralling humanitarian crisis, which has left 2.4 million people under siege, most of them displaced and crowded into shelters and tents during winter rains.
"Hamas people are hiding in their houses and the tunnels, while we don't find food or drink and are dying of cold," said Wojud Kamal al-Shinbary, who like many Gazans had made her way to Rafah, in the far south.
The WHO has warned of the risk of famine and disease, with only a minimal amount of aid entering.
On Tuesday the UK said a British ship had delivered 87 tonnes of Gaza aid to Egypt from Cyprus, the first shipment via a new maritime corridor from the Mediterranean island.
'Risks and consequences'
In the occupied West Bank, AFPTV images showed scores of people in the streets of Ramallah to protest at Aruri's killing, which Palestinian prime minister Mohammad Shtayyeh also condemned.
Shtayyeh warned about the "risks and consequences that could follow", his office said.
Israeli strikes in neighbouring countries on groups acting in support of Hamas have fanned fears of a wider conflict.
In a call with Israeli war cabinet member Benny Gantz after Aruri's killing, French President Emmanuel Macron urged Israel to "avoid any escalatory attitude, particularly in Lebanon".
A strike inside Syria last month that was blamed on Israel killed a senior commander of the foreign operations arm of Iran's Islamic Revolutionary Guard Corps.
British maritime security agency UKMTO reported explosions late Tuesday near a cargo ship in the Bab el-Mandeb Strait, between the coasts of Eritrea and Yemen, but said no damage or injuries were reported.
burs-smw/mtp
