Palestinian militants fired hundreds of rockets from the Gaza Strip into Israel on Wednesday, while Israel pressed ahead with a series of airstrikes that have killed 21 Palestinians, including three senior militants and at least 10 civilians. A state-run Egyptian TV station announced that Egypt, a frequent mediator between the sides, had brokered a cease-fire. But the truce efforts appeared to falter as fighting intensified late Wednesday, with neither side showing any sign of backing down. In a prime-time TV address, Israeli Prime Minister Benjamin Netanyahu claimed that Israel had dealt a harsh blow to the militants.