Israeli air strikes on Gaza City killed two Palestinians early Tuesday, while scores more were wounded when warplanes bombed two high-rise residential blocks, medics and witnesses said.
The raids came as Israel stepped up the pressure on Hamas on day 50 of a bloody confrontation which began on July 8 and has claimed the lives of more than 2,100 Palestinians and 68 on the Israeli side.
An early air strike killed two men in the street in the northern Al-Nafaq neighbourhood, medics said.
Some time later, another strike on the Nasser neighbourhood, also in the north, hit a 16-storey mixed-use complex known as "Little Italy", causing its complete collapse, witnesses said.
Medics said 25 people were wounded in the raid but no one was killed.
Witnesses said that F16s fired at least six rockets at the tower block, in which there were 60 apartments and a commercial complex including dozens of shops, completely destroying it.
They said residents had fled the building after the Israeli army sent them pre-recorded warning messages.
"The army told them to leave immediately and they all ran out into the street to find shelter," one told AFP.
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Shortly afterwards, warplanes fired on the 14-storey Al-Basha building in the western Rimal neighbourhood, causing massive damage and wounding another 15 people, witnesses and medics said.
Part of the building was used by Sawt Al-Shaab radio, or "Voice of the People", run by the Popular Front for the Liberation of Palestine (PFLP).
Hamas's armed wing, the Ezzedine al-Qassam Brigades, released a statement saying said it had fired four rockets at Tel Aviv and one at the northern port city of Haifa in response to the destruction of the two towers.
The Israeli army confirmed carrying out 15 air strikes since midnight (2100 GMT Monday), among them buildings serving as Hamas "command and control centres".
"Our forces also attacked compounds in two schools in the central and northern Gaza Strip that served as a centres for terror activity from which low-trajectory fire was directed at Israel," a statement said.
During the night, there was no rocket fire on Israel, but at 6:30 am (0330 GMT), militants fired a heavy barrage over the border, setting sirens sounding all up the Mediterranean coast, the army said.
Since then, 21 rockets have been fired at Israel, 18 of which struck the south and one of which was intercepted over greater Tel Aviv, a spokeswoman said.
She said there were no reports of anything hitting farther north than the southern port city of Ashkelon where a rocket hit a house causing major damage and lightly wounding 21 people.
Late on Monday, two rockets fired from Lebanon hit northern Israel, an army spokeswoman said.