Israel says it has launched a ground invasion in southern Lebanon against the armed group Hezbollah, marking another significant escalation of their long-running conflict that has heightened fears of a regional war.

U.N. and Lebanese security sources tell CNN that Israel has launched sporadic raid across the border, but has not yet launched a full-scale invasion. Jomana Karadsheh reports from Beirut.

Israel said commando and paratroop units launched raids into Lebanon on Oct. 1 as part of what it called a 'limited' ground incursion, while Iran-backed Hezbollah said it had fired a barrage of missiles into Israel.