TEL AVIV — A rocket strike Saturday at a soccer field killed at least 11 children and teens, Israeli authorities said, in the deadliest strike on an Israeli target along the country’s northern border since the fighting between Israel and the Lebanese militant group Hezbollah began. It raised fears of a broader regional war.

Israel blamed Hezbollah for the strike in the Israeli-controlled Golan Heights, but Hezbollah rushed to deny any role. Israeli Prime Minister Benjamin Netanyahu…