Three rockets were launched from Lebanon toward northern Israel on Thursday but landed in the Mediterranean Sea, causing no damage or casualties, the Israeli military said. A Lebanese security source said the rockets were fired from the Qlaileh region, south of the coastal city of Tyre, in southern Lebanon. Israel and Palestinian militants in the Gaza Strip have been trading fire this week in their worst hostilities for years. The latest incident did not appear to signal the opening of a new front. Israel fought a 2006 war against Hezbollah guerrillas, who have sway in southern Lebanon and advanced rockets. The border has been mostly quiet since then. Small Palestinian factions in Lebanon have fired sporadically on Israel in the past. A witness in the northern Israeli port city of Haifa said she heard three explosions shortly before the rocket salvo was reported. No sirens warned of the launch, something the military said was "according to protocol" - an allusion to Israeli air defences that ignore rockets set to hit unpopulated areas.