Hand-held radios used by armed group Hezbollah detonated on Wednesday across Lebanon's south in the country's deadliest day since cross-border fighting erupted between the group and Israel nearly a year ago, stoking tensions after similar explosions of the militants' pagers the day before.

A second deadly wave of unprecedented explosions in the strongholds of Lebanon's Hezbollah left it in disarray on Thursday, hours before a major speech by its beleaguered leader Hassan Nasrallah.