Israeli soldiers fought to repel Hamas militants Sunday and exchanged fire with the Lebanese militant group Hezbollah, raising the prospect of a broader regional conflagration a day after an unprecedented surprise attack on southern Israel by Palestinian militants that killed at least 250 and left Israelis stunned and reeling. The Hamas militants broke out of the blockaded Gaza Strip and rampaged through nearby Israeli communities, taking captives, including women, children and the elderly, while Israel's retaliation strikes leveled buildings in Gaza and its prime minister said the country was at war. Hezbollah struck Israeli positions in a disputed area along...