The airstrikes, confirmed by the Israeli military, followed Israeli air attacks a day earlier that killed two Islamic militants and touched off rocket fire from Gaza on southern Israel. The rockets caused no casualties but further ratcheted up frictions.
Gaza rescue officials said three separate airstrikes took place in Gaza City against training facilities of the militant Hamas group that rules the densely populated seaside territory. One set a nearby house on fire, destroying it and killing a 42-year-old civilian man, identified by health official Adham Abu Salmia as Bahajat Zaalan. Seven members of Zaalan's family -- his 65-year-old father, wife and five of his children -- were wounded, Abu Salmia said.
Fire also erupted in other houses and some were hit by shrapnel. In all, 25 people, including an infant, were wounded, seven of them critically, Abu Salmia said.
Gaza officials said an airstrike also targeted a Hamas training facility in southern Gaza, but no casualties were reported.
The Israeli military confirmed two airstrikes in all and warned that it would continue to operate against those who would attack Israel.
Hamas spokesman Fawzi Barhoum accused Israel of an "unjustified escalation against Gaza" and urged Egypt, the leading regional mediator in Palestinian-Israeli affairs, to intervene. He said the flare-up in violence was designed "to test the response of the Arab world ... to a future war against Gaza and against the Palestinians in general."
Yasser Othman, the Egyptian ambassador to the Palestinians, said Thursday that he had been in contact with Israeli officials and Gaza-based militants in an attempt to defuse the violence.
A burst of violence this week has shattered a recent lull along the volatile border area between Israel and Gaza.
On Wednesday, following Israel's expulsion of a Hamas lawmaker from Jerusalem, an Israeli airstrike hit a group of militants, killing one and wounding two others. Israel said it targeted militant squads that were preparing to fire rockets into southern Israel.
On Thursday, Israeli aircraft fired missiles at a car near a crowded park in Gaza City, killing two militants, including one from Hamas' military wing, and wounding five bystanders. Israel says the militants were planning to infiltrate Israel to carry out attacks.
Hamas has largely observed an unofficial truce with Israel since a tough Israeli military offensive three years ago in response to repeated rocket fire out of the seaside strip. But Israel says it holds Hamas responsible for all attacks that emanate from Gaza, and accuses the group of ignoring -- and possibly even encouraging -- violence by other militant factions.
Early last month, Israel and Islamic Jihad gunmen in Gaza engaged in several days of fighting in which some 10 militants and an Israeli civilian were killed. Israeli officials have threatened tough retaliation if the rocket fire resumes.
