Update: Reports now say Mohammed Deif has been killed.

GAZA/JERUSALEM (Reuters) - Mohammed Deif, the shadowy leader of Hamas's armed wing in Gaza, appears to have narrowly survived a fifth attempt to assassinate him, allowing the mastermind of the six-week war on Israel to pursue the conflict from his network of tunnels.

Badly hurt in repeated attacks over the past decade, Deif is believed to spend most of his time underground, overseeing the winding tunnels that have been painstakingly built over the past six years and were used to burrow into and attack Israel.

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Following Hamas rocket fire late on Tuesday, marking the end of a 10-day ceasefire, Israeli fighter planes bombed a house in northern Gaza, killing Deif's wife, his seven-month-old son and three other people. Deif was not there, according to Hamas, but his current whereabouts were not clear.

Hamas's military wing said it would "make an important announcement" later on Wednesday, but did not mention Deif.

The assassination attempt was the clearest signal yet that Israel regards him as the chief architect of the war, with the militant leader repeatedly catching his powerful enemy off-guard with surprise attacks that have caused heavy casualties.

Only last week, Israel openly threatened to track him down and kill him, having also announced that they had destroyed all of the 30 or so tunnels he had built from Gaza into Israel.

Deif's command position gives him an influential voice in the Islamist movement and whether it pursues war or truce. Yet after three decades of fighting Israel, he is still said to prefer his military role to any political ambitions.

Few people know what Deif, believed to be in his 50s, looks like today, after so many attempts to kill him. Despite having once been a stage actor, past images of him are scarce.

Rare video footage recorded in 2002 caught Deif covered in blood, sitting upright, dazed as a man tries to drag him away from the mangled wreckage of a car that had been hit by a missile from an Israeli helicopter. That was the first of five attempts to kill him, including Tuesday night's attack.

Hamas does not comment on Deif's health. It says only that he has been in command of its military wing since the 1990s.

Some Israeli reports say he is missing an eye, limbs and is confined to a wheelchair. An Israeli minister said last month that Deif had been in hiding in his own tunnels for years.

Nonetheless, Israeli intelligence officers are clear that he is playing a major operational role in the war. His tactics have led to one of the highest death tolls for Israeli forces, with 64 soldiers killed in the conflict, more than six times the number killed in its previous invasion of Gaza in early 2009.

Israel says it has killed hundreds of Hamas fighters and destroyed the concrete-lined tunnels, although Hamastook Reuters to see one of the tunnels this week.

"Deif pushed the tunnel concept," said Hamza Abu Shanab, a Gaza-based expert on Islamist groups. A Hamassource, who has known Deif since the 1990s, said Deif has been at the heart of developments inside the armed wing since 1994.

Ehud Yaari, an Israel-based fellow at the Washington Institute for Near East Policy, concurred. "Mohammed Deifhas been in a position of power the entire time," he said. "Some may not have noticed it because he has been hiding in the shadows."

SCIENCE STUDENT

Deif was born in Khan Younis refugee camp, according to the Hamas source. His family was poor and his father, an upholsterer, insisted the children pursue their education.

He earned a degree in science from the Islamic University in Gaza, where he studied physics, chemistry and biology. Deif also displayed an affinity for the arts, heading the university's entertainment committee and performing on stage in comedies.

He joined the then new movement Hamas during the first Intifada, or Palestinian uprising, which began in 1987, and was imprisoned by Israel in 1989, spending more than a year in jail, according to some accounts.

Rising up the ranks of Hamas, Deif has topped Israel's most wanted list for decades, held personally responsible for the deaths of dozens of Israelis in suicide bombings.

Yoram Schweitzer of Israel's Institute for National Security Studies described Deif's current role as somewhere between armed forces chief-of-staff and defense minister.

"His personal outlook and experience have made him a tough rival," Schweitzer said.

In a rare audio message broadcast on July 29, Deif said Hamas would continue confronting Israel until its blockade on Gaza - which is supported by neighboring Egypt - was lifted.

"The occupying entity will not enjoy security unless our people live in freedom and dignity," Deif said.

Despite having spoken out, Deif has no political ambitions within Hamas, according to Abu Shanab.

Hamas is a multi-headed organization, with most decisions made jointly by the armed wing and a political leadership that is scattered in Israeli prisons, Gaza, Egypt and Qatar, where overall leader, Khaled Meshaal, has been based since breaking with his previous Iranian-backed Syrian hosts in 2012.

"The movement rules, there are no surprises inside Hamas - no one leader takes a decision," Abu Shanab said.

Yaari, the Israel-based analyst, said, however, that Hamas's armed wing is "the main force" in its decision-making.

"Mohammed Deif has veto power, but he will not use it often," Yaari said, adding that Deif overruled Meshaal in accepting a previous truce that led to indirect Israeli-Palestinian talks in Egypt.

Deif's commander and mentor, according to Hamas, was Emad Akel, his predecessor as leader of its armed wing in the Gaza Strip. Akel was shot dead by Israeli troops in 1993.

Deif learned bombmaking from Yehya Ayyash, known as "The Engineer", one of the founders of Hamas's Izz el-Deen al-Qassam Brigades. Despite painstaking efforts to evade assassination, Ayyash was killed by Israel in 1996 in Gaza - by a mobile telephone rigged with explosives.

Determination - and caution - appear to be Deif's watchwords. Only last week, Israel publicly threatened to find and kill him, a threat it tried to deliver on.

"His nerves are made of cold steel," said a Hamas militant who has served under Deif. "When (he) decides to use a place to stay, he makes no movements. He is not curious to see the street. Instead he uses others' ears and eyes."