People search for survivors following a massive explosion in the southern suburb of Beirut on Tuesday. AP

Israel killed Hamas deputy leader Saleh Al Arouri in a drone strike in Lebanon's capital Beirut on Tuesday, Lebanese and Palestinian security sources said, as its tanks and warplanes pummelled Gaza in further "high-intensity" warfare against the Palestinian group in the enclave.

Arouri, 57, was the first senior Hamas political leader to be assassinated since Israel launched a shattering air and ground offensive against Gaza's Hamas rulers almost three months ago after a shock Hamas rampage into Israeli towns.

His killing could heighten the risk of the Israel-Hamas war spreading well beyond the Gaza Strip. Lebanon's heavily armed Hezbollah group, a Hamas ally, has been exchanging near-daily fire with Israel across Lebanon's southern border since the war in Gaza began.

Hamas radio and TV and Lebanon's pro-Iranian Mayadeen TV confirmed word from security sources that Arouri, a member of the Palestinian Islamist movement's politburo based abroad and a co-founder of Hamas' military wing, the Izz-el-Deen al-Qassam Brigades, had been killed when a drone struck a Hamas office in south Beirut.

In all, the drone attack killed six people in the city's southern suburb of Dahiyeh, a Hezbollah redoubt, the Lebanese state news agency said. Two security sources said the drone targeted a meeting and Hamas' Al Aqsa TV said commanders of the group's armed wing in Lebanon — Samir Findi Abu Amer and Azzam Al-Aqraa Abu Ammar — were among the dead.

Smoke rises from a destroyed apartment following a massive explosion in Beirut suburb, Lebanon. AP

Asked to confirm that Israel was behind Arouri's slaying, Israeli military spokesman Daniel Hagari told a media briefing: "We are focused on killing Hamas."

He declined to elaborate.

Mark Regev, an adviser to the Israeli Prime Minister Benjamin Netanyahu, said in an interview with MSNBC TV that Israel "has not taken responsibility for this attack."

"But whoever did it, it must be clear — this was not an attack on the Lebanese state," he said. "Whoever did this did a surgical strike against the Hamas leadership".

Reuters