GAZA CITY, Gaza Strip — An Israeli airstrike killed the commander of the Hamas military wing in Gaza Wednesday and Israel pounded dozens of targets in Gaza in the most intense attack since an Israeli offensive four years ago.

The killing of Ahmad Jabari marked a dramatic resumption of Israel's policy of assassinating Palestinian militant leaders and the Israeli military said it was the beginning of a major offensive codenamed "Pillar of Defense."

Palestinians called for harsh retaliation. The airstrikes came after a weekend exchange of Gaza rocket fire and Israeli airstrikes appeared to have abated. The Israeli offensive was likely to re-ignite the conflict.