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.

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 Hamas took 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 Hamas source, 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 Deif has 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.